Thank you! Sorry to hear you couldn't finish it.
As long as the host doesn't refresh their page, they actually keep the level progress upon reconnecting! It's a little unintuitive at the moment but you can do that. (After you've had issues you gotta enter the multiplayer menu to exit it again to enter it again to set up a new lobby...)
I'm sure with some more time, I can iron out some of the issues and add more failsaves!