Is it possible to fix this swollen floor?
Your floor is set too tight.  The manufacturer's instructions will have specified a gap--- perhaps 1/2" to 1/4" at the edge of each run.
As the wood accepts and releases moisture it will expand and contract.

Next time, finish the boards before you install them, and leave gaps based on the type of floor board used.

You can probably remove all those boards, discard the worst of them, then re-set them in there expanded state, and be fine.  For the exterior deck area, use boards without an overlapping groove, and leave enough space for water to drain off each board.  Probably use a single layer, not two, exterior.