Every bike regardless of design is to be careful matched to the purpose desired and the comfort of the rider. My frame, seat, and handlebars are precisely sized to accommodate my ample girth.
You will find the best position to fit you and your muscles will adapt with use. If a rear suspension is not feasible at least put some type of springing under your seat.
If the 65T chain ring is too big for the frame a smaller gear on the hub could let you use a smaller chain ring and get the same ratio. Either 42/13T or 52/16T will be the same ratio and should be readily available.