I have had good luck quilting in sections of about 18-24" wide. Did my Sylvia's Bridal Sampler that way and really enjoyed it. I added borders separately. Have you tried "borders by the roll" - these are pre-printed paper that you stitch on top of.

I quilt on my old Singer 15 that my dh bought me 37 yrs ago for $20. I put a big banquet table by it to support my quilt and it works like a charm! I can do all kinds of free motion. I have no desire to have anything else at this point, guess we all have diffrent ways.

Have you tried handquilting? We are all in such a hurry but it allows you to have a family life or even socialize while quilting. I can handquilt and watch TV or socialize with family and friends and it can be totally portable depending on the size of the project. Supposedly handwork is good for the bloodpressure. I handquilt on monday mornings at our local senior center with a small group of ladies. We spend about 1 1/2 hours actually quilting and manage to produce a handquilted bed size quilt that the center raffles off each year to benefit their programs.
I always take a small handquilting project with me when I travel. It is a great conversation starter on a cruise or while waiting in travel lounges etc. The only thing I machine quilt is for the Linus Project and those are all single bed or smaller sizes.

You can see the HQ sweet sixteen on their site handiquilter.com. It is a sit at system and not to large. I had its big sister the HQ16 midarm and now the HQ Avante that has a 18" reach. The sit down would be neat for you. Less $$ too.

Can't give you the topic, search the Board for a quilter who showed how she quilts from the front of the machine (turns the machine with the throat to the back). I have barely progressed to stitch-in-the-ditch so am not much help.