Can you wind the lower cutting blade to the right to cut less fabric and therefore fill out the stitching? On most sergers the lower blade position can be adjusted sometimes with a little knob or dial. You need to raise the top blade out of the way first, usually you put pressure onto it to release the spring holding it up against the lower blade, then swing it up to do this. Then wind the adjustment on the lower blade and move it to the right to cut less fabric then test serge. Your manual should give you more specific information on this and should be your first 'go to".
I would adjust my looper tensions to suit the fabric and width of the stitch I'm trying to achieve so yes, the settings you've been given are average tensions but its okay to vary these too. From left to right, I'd set 4, 4, 4, 4 and test serge again and see if this pulls the looper threads in against the fabric if moving the blade hasn't tightened up the stitching.
Sergers are more variable than a straight stitch sewing machine so its okay to move tension knobs a bit, just turn each a half number each time you adjust, then test serge and look at the stitch formation. Your needles tension should be fine at 4, leave them alone
I'd suggest if you can find one, go to a "Getting to know your serger" type class as there is lots of techniques such as seaming on a curve, turning right angles, both inside and outside and making rolled hem edges that are very helpful serger skills to learn along with making adjustments and troubleshooting. Or go to you-tube and search some of these techniques for videos. Also www.sewing.about.com
is a great sewing resource and Debbie has pages on sergers/overlockers here too.
When I'm starting a new dressmaking project I will spend 10 mins on the overlocker/serger, changing the thread colour to suit the garment, then test serging and adjusting the stitch tensions to suit the fabric. I have 4 cones of thread each in white, black, beige, grey, pink and pale blue and these threads will give a suitable finish on most fabric colours and prints. Then there is wooly overlocker thread, this is a fluffy thread that you can use for rolled hems as the thread relaxes once stitched and "fills" out the closely stitched edge covering the rolled fabric edge and is another whole area of fun to try out.
Often I'll just use a three thread to neaten the raw edges of a seam I will press open. Or I will assemble a whole knit garment using the four thread stitch, so much faster then stitching seams, then neatening. Jersey knits and sergers are made for each other.
As an aside the D on your machine model would denote "differential feed" too - briefly differential feed is adjusting the amount that the two feed dogs move under the foot and means you can "hold back" the fabric as it is stitched (0.5), or "stretch" it out (1.5 or 2 setting). Really handy for loose weave fabrics that stretch as you serge them, you can compensate using the differential feed setting. And in reverse, you can create a "lettuce" or wavy edge by turning the differential feed up.
I hope that this helps you out with your Brother 1034D and hasn't just confused you. Good luck.