Long term bottle storage from force carbonated beer

I made a stout that I was unsuccesful in bottle carbing. When I primed the beer was at 16%....I don't think there was any yeast left so after 3 months no carbonation. I just purchased a 2.5g keg with a mini regulator. I plan on openning my bottles and filling the keg.

What level should I carb my imperial stout at 25psi for a few days?

I also purchased the small C02 purge kit from williams brewing so I can purge the bottles prior to filling. I guess I can just use the racking cane method with a stopper to bottle.

My main question is...will I see any negative effects from bottling this way...keep in mind that I probably won't touch this beer for 1 year before openning and plan on aging some for 3 years or more.

This is my first time kegging or filling bottles from a keg so any tips are appreciated.

sounds pretty dangerous to me, its going to be hard to keep away the oxygen and keep everything clean enough to go through all the trouble to carb and rebottle. And the longer you store it the more risky it becomes.
I opened up a batch of barley wine once and dropped in carb tablets, and the tiniest bit dry yeast and recapped. It wasn't my best beer, but that did work ok. I'd do it that way if it was me

Maybe I'll try adding champaign yeast first to the bottle.