I agree with alot of what Pumpkin Patch said!
I've quilted several Queen+ on my regular machine.
I hope you don't give up on quilting due to this one experience. As several have said above, practice helps. Maybe, when you're done with this one you might want to try a smaller quilt or wall hanging until you get the hang of it.
A few other suggestions - SUPPORT! I have 2 tables around my sewing machine table when I quilt a big quilt. I put one to the left and sort of behind me and the other table I put to take up the quilt as it is quilted (imagine 3 tables in a row, one behind, then me and the machine table, then table to catch the quilt in front). Trying to hold up the weight of a quilt all rolled up and move it and quilt it can be tiring.
Take frequent breaks. I try to quilt for 20 minutes and then stop and get up and stretch etc. It will help some.
When you make your quilt sandwich - I can go a bit overboard here, but my first big quilt shifted and I had heartache. So I baste my quilt and then I pin it to death. I probably over-pin but when I'm wrestling with it trust me it doesn't shift.
I too start in the middle and work out. After I do a section or a line or whatever, I remove the quilt and flip it and make SURE I didn't pucker etc. (don't know if that is the correct word).
PROMISE that if you stick with this, each one gets a bit easier. It is doable on a regular machine, but it will take some patience.
Your quilt is BEAUTIFUL and you obviously have talent - stick with it!!!