Questions about starting resistence exercises

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Sorry for all the questions. Thought I'd get this all out in one shot. I'm really interested in others perspectives on my exercise regiment.
I do all of my workouts at home. I attempt to do at least 60 minutes of cardio a day. I don't belong to a gym anymore. But I do want to start resistence activities at home. I do have some questions:

1. What home resistence activities would you recommend? What I'm doing for upper extremities is pushups and reverse pushups off of a chair to target triceps. I do pushups and reverse pushups 3x weekly. I don't count but I still have to do the "girly" pushup but I just do them until I can't do them anymore. Basically 10 minutes of each (working on increasing that time).

2. Should I invest in some different hand weights? Or will the exercises I'm doing suffice? Right now I'm doing 30ds with 8lb handweights. I have those and the 3lb weights. Could I use those effectively? I also try to fit in kickboxing 2x weekly using the 3lb hand weights.

3. I need recommendations on how to target my legs? Can I just use my own body weight as resistance? I ride my mountain bike daily which gives my legs a great workout, but I want to start toning and building lean muscle.

4. Abs: I'm doing basic crunches and reverse crunches. Any other other suggestions? I've had several abdominal surgeries so my abs are pretty weak. But I know you need to strengthen your core. Any workouts you'd suggest? Home programs?

5. I have about 75 more pounds to go to reach goal. Should I focus on cardio or do you think it's wise to start inserting some resistence training with the cardio like I have planned.

Any advice would be much appreciated.