I cannot find in the manual how to set the camera to film a theaterperformance?

I assume that this is a film camera that has light meter.
It could be that the camera is set to a different film sensitivity than the actual film.
For example, the film is 400 ASA but the camera is set to 100 ASA.
The sensitivity rating of the film is written on the film box and on the film cartridge. Make sure you set the film ASA number on the camera too.

At the theatre prior to the performance, ask the lighting director to show you one of the brighter performance stage light configurations and allow you to set the camera's white-balance. (It's easier to deal with a little under-exposure in post production, than it is for over-exposure.) Then adjust the exposure accordingly during the performance.

Preparation/Planning: Either at home or in the theatre, if you practice setting the white balance and then adjusting the exposure for varying levels of light, with your camera connected to a video monitor, so you will see it more clearly in real time, it will help adjustments during filming the performance more fluid.

Also consider using a lens filter. Practice various combinations to see what suits different light levels and gels for best effects. When possible, if using a stand alone camera (not cabled into a control room set-up) I prefer using a video monitor for each camera person to give better ability to manage adjustments of camera settings as needed.

Yes. You have full control over the shutter speed and aperture in the Manual exposure mode, as described in the "M Mode: Manual Exposure" section in the manual.

You also have full control over the focus, as described in the "Manual Focus" section in the manual.

If you need a manual, you can download it (in two parts) from
http://ca.konicaminolta.com/support/manuals/film-cameras/film_af_slr/index.html

ISO and aperture are most definitely not the same thing. ISO is the speed of the film. Aperture is the size of the opening in the lens, the larger the opening the more light comes through.

To change the aperture in Manual mode, hold down the exposure compensation button near the lens mount and turn the control dial on the front of the camera.

Slide the camera back lock release down, open the back, and pull out the film cartridge. Full instructions are in the manual. "LOADING FILM" is on page 16, "REWINDING FILM" is on page 24, and page 25 shows how to remove the film.

If you need a manual, you can download one from
http://butkus.org/chinon/nikon/nikon_n70/nikon_n70.htm

With the camera turned on, look in the viewfinder. Down on the bottom right side is an LCD display, if it's blank then your camera probably has dead batteries. It takes 2 x CR1/3N or 4 x SR44.

Your film accepts 35mm negative film or 35mm transparency (aka slide) film. It will accept any ISO from 12 to 3200, but in practice all you'll usually need are ISO 100, ISO 200 or ISO 400. You choose the film based upon lighting conditions and the lenses you'll be using, but in general you'll use ISO 100 if shooting mainly outdoors in daylight, ISO 400 if shooting in low light or with a telephoto lens, and ISO 200 is a general all-rounder good for most things. ISO is usually referred to as film speed as higher numbers need less exposure than lower numbers but the trade-off is a less detailed image.

To load film into your camera and to set the camera to match the film ISO setting refer to this link to the manual provided by Norman Butkus. The manual will also guide you through all other aspects of operating your camera.

I hope that I have fully answered your question, but if not please add a comment and I shall respond in due course. If your question has been answered, then please let me know by taking a moment to rate my answer.

You'll find a full manual from http://www.pentaximaging.com/support/manuals-and-literature/

You should have a proper lens attached and the film loaded before you can take pictures.

Generally when a camera refuses to take the photo is because you are operating beyond its expected lighting settings. If you are on automatic, it will just flash a light at you, or give you some indication it is beyond the limits of that setting. Try manual, or some other setting like landscape, or backlight. Generally this will happen on automatic settings. 
Film? Try the f16 rule. In broad daylight, the rule is use f-16 and a shutter speed that matches your film's asa. So 100 ASA film? Shoot the sunset at 100th at f-16. Darker, open it up two or three stops. f-11, 8, or 5.6. 
Bottom line, make sure you are on manual. The problem is likely an automatic exposure. 

Did You ever use a SLR back in the stone age when all we had was film?
Film was/is rated with a ISO number, the higher the number the faster the film.
Fast film had fewer and larger grains of silver iodide, (the particles that changed tone, color etc.when exposed to light), therefore it took less light to take a picture.

The down side was a increase in grain. Large grains meant that blow ups, 8x10, 11x14, posters, etc were not as sharp,
as with slow ( low ISO film)
Most outdoor photos had plenty of light so the film had more grains ( high ISO) to capture the available light, and the result was a much sharper image.

Portrait photography used very very slow film ( your 50 ISO setting) but in a studio you had all the artificial lighting you needed, so your portrait came out with very fine detail.

Now the FE-280 does not have a shutter setting, but we can compensate by changing the ISO setting, and the overall effect will be.
Fastest= 1600 ISO for very little light and poorest picture quality.
Slowest=50 ISO for plenty of light and the highest picture quality

200 ISO was the most popular because it worked well outdoors and indoors with a flash, with very good overall picture quality.

400 ISO was a good choice for gloomy days and medium lighting conditions.

Your ISO settings on the FE-280 will have a similar effect.
My best advice is to play around with the different settings until you develop a knack for it, we used to use light meters and a lot of guesswork, quite expensive when you had to buy film and pay for processing.

OK enough history. heres how....
Turn dial to (P) PROGRAMAUTO
Press (MENU)
The camera menu in center is bracketed, Press (OK)
Scroll down one bar on the on screen menu to (ISO)
Press (OK)
Scroll up or down to desired ISO
Press (OK)
TAH DA !

All other functions will be automatic or any other setting that you might choose..
If you change the dial and later go back again to (P) it will retain your selected ISO setting, which is displayed, on screen.

I hope I was help full, and you enjoy some of the special effects that you will now be able try.
By the way... good taste in cameras.
Best regards, Paul

Your camera is cocked but since the shutter is not working you cannot release it and hence your film advance mechanism does not work. ME-super will work without batteries in full manual mode so set your shutter to B and try to release it. If the shutter will not release in B mode then the shutter/mirror box will need servicing : rubber components in the mirror box mechanism have perished and need replacing. After that your camera will be fine for another couple of years.