Why are you against a mountain bike? When I returned to cycling, it was on an '86 Diamond Back MTB. Put over 1,000 miles on that before deciding to switch to a road bike. At your weight, an MTB with narrow slicks would be a great choice. As your budget is limited, your current bike, with a few repairs, may be your most economical option as well. If you want to be a bit more upright, swaping the stem and/or bars can do that on what you have. Then do some riding, start socking away a bit of money, drop some weight and see where it all leads you.