To strengthen your legs those are all fine, obviously not as good as with weight machines, but are still very effective if done correctly. If u want to get more out of it, try incorporating the dumbells into the workout, like holding them when you lunge or wall sit

If you run you'll get lots of muscle im in track and I didn't lift at all and I had the most defined and rock hard quads I've ever seen and im in the gym daily now. I'm a thrower and need a lot of leg muscle. My trainer has me doing squads and every form of it between squat jumps to deep squats to squats the you bring your knee to your chest. If you look up leg work outs you should find good stuff. But I think running made my legs the strongest they have ever been.

Yes, running stairs and doing plyometrics will work.

Ride a bike uphill you dummy .

On weekends i dont have much weights (only dumbbells) to workout with. Is it possible to get stronger and bigger legs for football by doing exercises like; wall sits, lunge jumps, hill sprints, duck walks, etc.?