Zero reason to wait until you're at a certain weight or hr to do a ride. Do hill repeats now. Do a 30 mph loop as fast as you can once in a while. Change things up. Have fun with it all. Doing the same thing repeatedly while waiting for results is really boring and not conducive to long-term improvement.

Also, weight loss happens in the kitchen, not on the bike, so I wouldn't worry about trying to do "fat-burning" rides. Those don't really exist. You burn calories, you consume calories. Make the latter slightly less than the former.

Good luck, have fun! Maybe find a group ride to join, too.