I really like now nice it looks. You did a beautiful job on it.
The 2x10's might last forever, or they might sag on you. Worse case is that one will crack and fail on you. If it was me, I would double up on them and use liquid nails to glue them together, and screw them together every foot, top and bottom, with deck screws.
I would use three lags bolts at the end, or drill all the way through the tree and use two half inch or larger bolts at the end of each board.
How did you attach the floor joists to the beams? If you just nailed through the end of the beam into the end grain of the joists, then they will come loose as the wood dries out and the deck moves. Joist hangers would be the best thing to use. You can add them in there easy enough. They make them with angles too, so you should be alright there.
You probably need to spend a couple hundred bucks more to get it there, but then you should have peace of mind for a couple of decades.
Eddie