That tire is not a bad choice. It does have much less resistance than the old " mud-grips " that probably came on your bike. You've already cut the rolling resistance down a lot. My converted mountain bike has a very similar tread design but it is 1.5", which should fit yours. In my opinion, since you may be trading soon, I would just go ahead & try to use your present tires. Swapping out will not make that much difference. Keep an eye on tire pressue. Practice,,,, do leg strengthening excercises,,,,
continue dieting,, & all that should help a lot.