Hi Tom,
I'm not sure what to tell you other than what I've learned over the years and what we do, but I'm not an expert by any means. I receive SSDI also and my husband works. We have a small tax firm in our town that we use. We file jointly because it has always saved money over filing separate for us, (and everyone else that we know of), regardless of income. As far as long, short, or EZ forms; our tax preparer usually files either short or long, as the EZ form is usually for single people who don't own any property. Mortgage interest and home improvements, (especially green in nature -pun not intended), are both deductible if you own your home. It also depends on if you have private insurance or medicare and what your out-of-pocket expense is for care and medicine, because you can deduct it if it what you've paid exceeds a certain percentage of your income. We were also able to deduct travel and hotel expenses when I had to go to Mayo Clinic in Minnesota for care.
I do know that as long as you file income from your home office you can deduct all supplies as long as you kept receipts, (in case you get audited). When Frank was a house painter we claimed all his work clothes and shoes. If you don't claim income, I don't think you can because it's considered mainly as entertainment.
Luckily our tax lady figures both short and long form for us, and files whichever costs us less money or gets us a bigger return, without charging us an arm-and-a-leg. (Thank goodness cause I can't afford to lose anything else
.) They are also saying that the stimulus checks are complicating taxes for 2008, so unless you're really good at understanding the tax laws I'd look for someone who knows them so you guys don't wind up in trouble. You should be able to call around in your area and ask what different places charge for filing the different forms and if they will support you in case of an audit. Hope this helps and you both are doing well. Terry