Chair-assisted strength circuit for 60+

I'm a man in my early 60s, new to (or returning to) exercise, with no gym kit. I want a 25-minute chair-assisted full-body strength circuit that's gentle on my joints and heart. Use a sturdy chair for support and balance. Please give me: 1) A 4-minute warm-up: marching in place, seated arm circles, ankle rolls, and gentle shoulder rolls, with seconds for each. 2) A main circuit of 6 exercises, all chair-assisted or supported where balance is a concern: chair-supported sit-to-stand squats, wall or counter push-ups, chair-supported single-leg heel raises, seated-to-standing rows using a towel for tension, standing hip hinges holding the chair back, and a chair-supported step-back lunge or marching. For EACH exercise give me sets, reps, rest in seconds between sets, and an effort target in plain terms (I should stop 2-3 reps before I can't do any more — never to total failure). Aim for 2 sets of 8-12 reps each, 45-60 seconds rest. 3) A 2-minute cool-down with gentle standing stretches, with hold times in seconds. Keep instructions simple, tell me how to breathe (exhale on the effort), and flag any cue that protects my back or knees. If anything raises my breathing too high to talk, tell me to slow down.