RE: How to avoid "spin outs"?
Your description of "pushing" over the top of the fin does not sound quite like what I'm suggesting, and "pulling" toward upwind with your back foot is only something I would suggest to "recover" a fin that's already "spun out".
So, try this on your next sesh.
Get your board going as fast as you can on a beam reach (straight across the wind at 90 deg.).
Then begin to lift (not pull) a little with your front foot in the front footstrap to get the upwind rail up slightly higher than the lee rail.
Now begin to "push" across the top of the fin with your rear foot.
Imagine that you are trying to push the board away from you straight across the top of the water.
You can determine which rail is lowered, and how much waterline length you have in the water by looking down at your board momentarily.
If the "splash" of spray and white water is coming out from under your board on the upwind side, and you see pretty much "green water" (no splash) off the downwind rail, you have it right.
Notice the place (along the rail of the board) where the "splash" comes out from under the upwind rail. If you can get the splash to come out from under your board at or behind the front footstrap you have it right.
If the splash comes out forward of the front footstrap, your board is riding too low at the nose. Maybe move your mast foot back a little and see if you can get the exit point of the spray to move back under the front footstrap.
Also, try giving your sail a little more downhaul, to make it slightly less powerful, or get an adjustable outhaul "kit" so you can have your sail be really powerful to get planing and less powerful and more "slippery" once you are on plane and the apparent wind has accelerated due to your forward speed.
Also remember, (esp. on your smaller boards and fins) that if you are feeling alot of pull with your back hand, that force needs to go somewhere, and it travels from that back hand, through the arm to your back shoulder, down through the torso, and down your leg to the foot in the rear footstrap.
So you may want to change your mast foot postion, harness line length, boom height, and trim and tuning of your sail to get that pressure off the back hand and hence off the fin.
Hope this helps,