I think the braking action is probably more a function of the setup and stuff than of the type of brakes. I've been riding bikes with disc brakes for several years. I just bought a new rim-brake bike. Brakes on it work great, no real difference in feel from disc brakes. Yes, either one could be adjusted so that they suck, but they don't just inherently suck because of what kind of brakes they are. One thing to try is applying JUST the rear break and JUST the front brake and see if both seem to be pretty functional or one is not doing much of anything, and that'll give you a good place to start adjusting.
My saddle experience- first bike I bought was a $100 mountain bike. Saddle was like sitting on a 2x4. So I bought a big cruiser saddle for $20, that fixed that. Next bike was Worksman cruiser that came with the big cruiser saddle, so no problems there. Next bike was a Raleigh Sojourn that came with a pre-aged Brooks saddle. That was a narrow little saddle, but more comfortable than any of the others. So I assumed that the saddle on the $100 mountain bike sucked because it was a narrow saddle, and no, it sucked because it was a sucky saddle, not because it was narrow. Anyway, the saddle needs to fit under the sit-bones in your butt, and being heavier doesn't necessarily make those bones any bigger, either. If the wider saddle works, fine, but don't assume that you require a tractor seat just because you weigh more.
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