Apollo 250RX db-36 front and/or rear sprocket changes for torque & part selection

[Apollo250RX]

I want to change hearing for more torque and less top end.
I clocked the bike at 62 wide open.
I would like more low end torque.
Where can I buy compatible sprockets for the 250rx Zongshen ?

Should I go to a 13t front and keep the stock rear?
Can I do that and keep the stock size chain?
I want to lose topspeed a little, and only gain a little torque.
Please chime in.
Because I believe the parts availability limit the gear ratios.
I don't know.
Do other make bike sprockets work?

Please let me know.

I'm also wanting to change the rear strut.
Hopefully just a part swap if possible.