I agree with Jughed about correlation, or lack there of, between movements with machines versus free weights. I would continue doing squats at whatever weight I can handle, for whatever prescribed rep range you choose. Heck, start with just the bar and go from there. I would also suggest using front squats into the mix as it targets slightly different muscle groups than the back squat. You will not be able to lift as much on the front.

I've never been a fan of the leg curl either, and other isolation movements in general, for that matter. I've read some damning things about this particular exercise as well. Doing something like a Romanian dead lift might be a better option to work the posterior chain.

With only a bar and some plates you can do so much for your lower body. Add a squat rack, and the you've got even more options.