As far as core strengthening exercises, it's perhaps difficult for me to judge how much they help because I have always had a strong core. But here is what I do. Monday, Wednesday, Thursday, Saturday
1) Lay on side and do sideways leg raises. I raise my leg sideways as far as it will go without too much effort then bring it back down then bring knee up to chest then back . I started at 10 but now do 20 both sides
2) Lay on back and bring one knee up getting foot as close to butt as possible hands at sides I raise the other leg keeping it as straight as possible. I also started at 10 and now do 20 both legs.
3) Still on back I put both legs straight and raise one up keeping it straight and do both legs 20 times
4) still on back I raise both legs 6 inches then spread them sideways as far as I can go then back together then bring my knees up to my chest to relax a little not letting feet touch the ground then repeat 10 times
5) Standing I roll my head/neck around in a circle 5 times each way
6) Standing I push my hips forward and move them around in a circle 10 times each direction
7) Standing I move my knees around in a circle 10 times each direction

I stand with my feet wide apart and crouch down over one knee while dropping my knee on the other leg then without coming back upright I move my body over the other knee and drop the original one to ward the ground. I started at 10 and now do 20.
On Tuesday and Friday I do all the standing exercises above and also do these core plus balancing exercises
Standing I bring one leg up forward as far as it can go and then back down without touching the ground then I bring it up sideways as far as it can go and back down without touching the ground then I bring my knee up to my chest and back down without touching the ground, then I move my leg backwards as far as ti will go and bring it back. If I touch the ground then it is okay but I will repeat the whole process if I don't complete those 4 maneuvers without touching the ground. And I do 10 for each leg. Rarely I can do 10 without touching the ground . I also do dumbbell weights on Tuesday and Thursday.
I would say those exercises keep my core fairly strong. I 'll let you know what I am doing for my shoulder in another post
So what is worse.... dying or regretting it for the rest of my life? Obviously I chose not regretting it.