Cheese grater stirrup pads are the best! They helped stabilize my leg and foot a lot before I got my free jumps!
Different stirrup pads could help a lot! Usually the white rubber pads are not very stable and make it easy to lose your iron
I got grippy pads that helped a lot. For losing your stirrups, try different stirrup pads and try to put your foot farther into the stippup if you are not on the ball of your foot. As for longer stirrups, try going with out them or just putting then down a hole or 2 and practice that way.
put more weigh and pressure into your feet
you are either riding with too much pressure in them or not enough. put eggs in the stirrups. you should have enough pressure to hold the eggs but if you break the egg then you have too much
Put dollar bills underneath the balls of your feet 😉 You could also ride in a bareback pad if your horse is well behaved enough