You see that chipboard in the background? It will never look the same again. Same might go for the ceiling. Definitely search blowoff tube. Not OK to leave it like that. You can get some cheap vinyl tubing and put it right over the inner tube int your 3-piece airlock, or jamb a piece of tubing into the bunghole (that's what I do).
Right now, remove that airlock and bung and put a piece of foil over it. Set the whole thing in a garbage bag until it settles down. Then put the cleaned bung/airlock back in there.
Here's me filling mine too high (have to watch to the end). Way too high. Me dumb. (BTW, all of this gear and the methods and mistakes have been replaced with better gear and methods and mistakes).
Regarding headspace, I don't think it's a terrible thing to fill it near to the top. It does mean you'll lose a little bit (or a lot) to blow-off, but as long as you're prepared to handle that, it only means a bit of an efficiency loss.