(1) You can dump the heavy weights, and do bodyweight pistol squats...It requires MORE strength, coordination, balance, mental focus, flexibility...Overall, it is a better exercise...
You are building strength with that excess load on your knees...
When that gets easier, you can add dumbbells or kettlebells
(2) Like I said, if you are 30 and up, dump all that heavyweight training...Focus on body weight, flexibility and cardio...You don't want to be a 300LB stiff 60 year old...
First, you need some cardio to improve circulation...Soccer and basketball are great for this
Second, to build REAL strength you can do the following
Biceps - Pull ups
Triceps - Dips, variations of push-ups
Chest - Push-ups
Back - Chin-ups
Legs - Pistol squats, wall squats
Third, to maximize your range of motion you can do Yoga
If you are 30 and you do these exercises REGULARLY for 30 years (with good nutrition and rest), You will be LIGHT, strong and flexible by the time you 60...Much better to lean flexible and REAL strong, than to be 300LB of flabby muscles and stiff joints...
I worked as a physical therapist in a Nursing Home, my observation was people who were old, stiff and heavy had a decreased quality of life...