Rotator cuff (I think) and footwork

First the "tale of the tape". I'm 42, 208lbs and due to a couple of herniated lower disks I have very little flexibility. I started using the Body by Vi shakes and in the last few months I'm down from 226lbs in April. In that time I have fallen in love with exercise again for the last few weeks I've been hitting the heavy bag (with wraps and 14 oz boxing gloves). I don't have the budget to go to a boxing club so my "coaches" have been a few boxing forums and youtube.

Now for the newbie questions.

1. Punches - I think I've been stressing my rotator cuffs because it's tough to raise my arms the next day after punching the bag - not enough to consider it an injury but I definitely feel it for a few days. I absolutely love the snap and pop of my punches so I want to keep heavy bag training so perhaps a few tips?

2. Footwork - For the life of me I cannot seem to do anything but play "paddycake" with the bag. I need to incorporate head movement, footwork, bobbing/weaving instead of standing there throwing punches. Ideas on how to coordinate my hands, feet and head?

3. Shifting weight - I am an orthodox puncher and I've read where when you throw a jab you step forward with your left foot and push off with your right foot. But in order to follow up with a cross or right hook I should have my weight on my right foot and transfer it up through the hips. I am not sure how to do this/

I appreciate any help or advice. Thanks!

Stretch your pecs, traps and deltoids after a boxing workout and see how it feels, also make sure to include a rest day or two... Or at least a day where your shoulder joint isn't under stress... Jog or cycle or skip etc.

Constantly pounding a muscle group day after day with the same repetative motion is bound to lead to tightness and soreness.

For the basic stuff in my opinion the best place for self learner is Kenny Weldon :)

For the punching problem i can imagine two-three things.
First you punch with alot of overhand type of punches without the necesery flexibility
Second the sholder problems are related to the back problems... The herniated disks may force your posture in bad possition or the oder way around...
The third you push the bag too much and this results in overstressing the sholders. Here you don't thing the sport of boxing as a sport. In all sports the ideia is to move fast some kind of inertia. In boxing you try to rotate your body as fast as possible, which leads that the bag is not there to be pushed by you, but just to stop you... In this way of thinking the sholders are there to possiotion your hand to transfer the rotation impuls into the punch and not to create additional power.