I really appreciate your passion about this project. Changing engines is way harder than one can think as every engine handles things differently and has a different workflow. You should first change the engine when you find one you're comfortable with. Porting the game now will be too much of a chore, except you decide to remade it for a fourth time.
I still expect that the whole Unity situation will get worse and will force you to change, but I do hope it will be after you finished this game.