I am relatively new to needle punch; keeping fabric tight was a major problem for me. My solution:

Another problem is buying balls of 3-strand pearl cotton floss in store, rather than online, and single quantities. I will have to think on this a bit, I am working my brain to the bone as I type!

I LOVE doing punch needle!!!
I use a Morgan Lip Lock hoop, definately keeps the fabric tight, which is soooo important. Also, I really like using Valdani floss, which comes in 3 strand balls. I buy most of my supplies at "Country Stitches" online. You can get everything you need there, and the prices are reasonable. Just do a google search. Balls of Valdani can be purchased in any quantity. The webstore is run by Brenda Gervais, she designs some FABULOUS primitive punch needle designs and cross stitch patterns. I love her stuff.
What kind of fabric are you trying to punch on? I have only punched on Weavers Cloth. That's what your fabric looks like, but not sure with out being touchy feel-y.

Not sure why you are having troubles with the loops not holding, especially if your needle is threaded properly. Sorry I can't fix your problem, but hope my other suggestions help!!!

Want to do a small rug with rug yarn but not too sure what to use as fabric base. Burlap? Monk's cloth? Any ideas?