Thoughts on swapping rear sprocket AND rear tire size

smaller wheels should add to torque, but will reduce top speed and thus decrease mpg. just food for thought.

Kickstart, I am in nearly the same situation as far as hills and weight go. I'm at 190 with a 48cc two stroke on a cruiser to which I've added a few things. I'm running a 44t now. I'll work on dropping a few pounds later but one thing I did that helped is I switched to a tire that can be inflated to higher pressure. If you are rolling on mountain bike tires that will make it even worse but the point I'm trying to make is to reduce rolling resistance. Skinny tires, high pressure, slick pattern if possible but you will have to decide. The harder the tire the rougher the ride and the narrow profiles don't do well on soft shoulders.

if they supply a stock 44 tooth,then a 60 will be 30+ % more power,or it will behave like its lost 1/3 of the total weight of the bike and rider.
but 1/3 slower.but it will make higher rpm's.
the tires i look for,in my honest opinion should have some kind of smooth rib down the center.anything is better than a mountain bike knobby.
i havent installed my 50 tooth sprocket yet,but hoping it will help me some.

The stock gearing is about 18:1, good for 26MPH (~42KM/h) @ 6000RPM.
A 24" wheel would make that 24MPH (~38.5KM/h) @ 6000.

Switching to a 60T sprocket with 26" wheel will change the ratio to 24.6:1, which is 19MPH (~30KM/h) @ 6000.
A 24" wheel with that 60T would reduce it further to 17.5MPH (~28KM/h) @ 6000.

How steep are these hills exactly? I never had problems climbing steep hills with a 26" wheel and 44T with some pedaling.
A 48T and 24" might be your best bet, IMO. That's 19.68:1, 22MPH (~35KM/h) @ 6000.

other options are an expansion chamber or if you are driving a bike with gears, a shift kit is also possible.

I weigh 210 lbs & I don't have that much trouble climbing hills with a 40T, 26" wheels & a 66cc engine.
I would think that just a 48T & some proper tuning will get you the power that you need.