I'd get a new tree and start over, because a 25 ft cherry tree is the real problem.

I have Stella. Bad cherry in my opinion. Go get a Lapins or Black Gold... Stella is one of the older cherries and it just compete with some of the newer ones.

Chop it and replace with a new self fertile cherry. Get something on Gisela 5 if you want it to be dwarf.

That's up to you, Stella is self fertile, ..it seems you got quite a bit of room so this is what you could do, let your leader come off higher which is better for deer, get another tree and plant it close, now you have two trees side by side and you can compare over the years how they do until they have fruits.
Then chop the one down which doesn't perform to your likings.

I think it's fairly obvious that you need a deer fence, especially if you plant a new tree. But even if you keep this tree the deer will likely ruin it this fall as they rub their horns. Once it gets big you could keep it unfenced as long as you are OK with a big tree.

You need a circle of fencing about 5ft tall supported by T posts.

I just make a loop with farm fencing 5 foot tall and weigh it down on the bottom wire with two rocks or wood planks, this way I can easily move it when I have to work in there.

Thanks for all the good advice. I think I'll try a new tree and put some fencing around it!
Thanks all.