As for #1, one can see how you might be stressing your left knee.
1. You seem to take a stance with your feet rather far apart. IMHO that tends to restrict movement and to put more stress on your knees when your legs are active during the swing. You might try taking a somewhat narrower stance and see if it helps. I have a bias toward a narrow stance.
2. Looks like your feet at a right angle to the address position. It is most common to either have your right foot at a right angle perpendicular to the line of address (I get weird and actually may have my right foot pigeon-toed and angling to the target and my left foot perpendicular) and your left foot splayed left between 30 and 45 degrees, OR to have both your feet pointing out slightly. IMVHO that is a matter of comfort and not mandatory to a good golf swing, though for learning purposes it is better to try what pros do first. But you might experiment a bit with foot angle and see what feels best.
3. It looks like your legs are very active in your swing. I don't think that's a bad thing necessarily, though others on here may have a different opinion. The older style swings did use the legs a lot. The modern style is to keep the legs quiet and to get your swing arc out of the shoulder turn and not by using the legs; the power of the swing comes from the angle of the shoulders vis-a-vis the pelvis, and some power players keep their pelvis and feet open while taking a gigantic turn the other way with their shoulders. So you could concentrate on your shoulder turn and limiting the motion of your legs and pelvis to stress your knee less to help your knee.
Question #2. This is outside my expertise, but that won't stop me from commenting. Most folk on here will tell you there is a right way to swing a golf club and a wrong way. I suggest that whatever gives a good result is fine, whether you swing like Jim Furyk, Miller Barber, Ray Floyd, or Bobby Locke. Those guys made good money out of swings that would give a modern golf pro nightmares. Arnold (Palmer not Schwartzenegger) said to take a good grip and keep your head still and not to worry about what goes on in between. Reassuring advice that is not always correct. But everybody's swing is different, thank goodness.