Wow. I somehow managed to finish 35 with an extra control up my sleeve. (The Lava was hot on my heels)
Strat was simply to isolate the bottom two sources, and try to outpace the top right. When I came to the two bonus keys, I realised I may have fallen into a trap; but I saw that I only needed to paste the tile arrangement I was using to continue running to the exit over that gap by the exit just once.
Even though I just completed it now, exactly what I copied is a bit hazy. I think it was a group of tiles in the area of the bottom right-ish of the map.
All in all, a very nice little puzzler. Well done! I can tell a lot of love went into making this. :)