My hayward ec 40 is leaking water out the top where the handle is

Replace the O-ring.

Copy following link for hayward product manuals, and contact-us link:
http://www.hayward-pool.com/pdf/manuals/PowerFloLXandPowerFloII.pdf

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

Water in the pressure gauge indicates a faulty gauge. It will need to be replaced. They usually run $10-15.

I USE MAGIK LUBE ON MY O-RINGS, THIS HELPS THE O-RINGS SEAT PROPERLY

Here is a copy of the users manual for these pool filters. It has detailed illustrations about how the filter should be put together.

http://www.backyardcitypools.com/images/hayward/perflex-system-manual.pdf

A better way to clean the filter tubes in the EC40 is to remove the filter tube assembly and soak it in a 5 gallon paint pail that is filled with a solution of water and a 20% muriatic acid, available at hardware and home center stores. Be very careful handling the muriatic acid. Don't splash it around.

Mix it in a 1-to-1 ratio with water and soak the assembly for at least 8 hours. Keep the soaking pail out of the reach of kids and animals.

Remove the assembly, properly dispose of the acid mix and refill the pail with clean water. Soak again for 3 to 4 hours, then reassemble your filter.

Some pool guys say it isn't necessary to soak the tubes in clean water because the muriatic acid will not harm the pool water and will reduce the pH if it's too high. I've always soaked them to be safe.

This is a link to the Hayward manual that describes the process:
www.haywardnet.com/products/Manuals/pdfs/manual9.pdf

make sure the gasket around the tube sheets is secure

You have a leak, if DE is getting back in pool your filter is either dirty and needs to be taken apart and throughly cleaned, or you have a ripe in one of the DE cells. The pump not priming is a leak somewhere before where water enters pump. Could be a bad o-ring in a valve. Hard to tell what is is without troubleshooting, piece by piece. I would start with cleaning Filter first.