I know, I still wasn't able to make enough bars for anything cool even though I blew through half my potion stock.
The obsidian was easy to come by, the problem is that I take to much damage from the deep monsters and I can't harvest surface shrooms fast enough to keep my potion stocks up.
Tends to be a lot more efficient to just buy lessers and set up a decent sized glowing shroom farm, instead of bothering to harvest the surface shrooms. It's
really easy to make an industrial-scale farm that'll keep you in the glowfungus indefinitely. If you make it large enough, you can pretty easily use the excess shroomage to supply the coin for the other half of the ingredients.
As for hellmining, the usual applies. Knock th'fireballs out of the air, pave over the lava (oh gods, do not leave open lava pits), keep an eye out for th'serpents, and don't try it on MP. Hellmining is for singleplayer *nods*
You seem to have got all that, though. Maybe invest in th'autoclicker and a decent speed weapon, if you haven't already, to keep the fireballs away? Or hunt down a balloon -- I find the serpents easier to avoid with that than th'cloud, and easier again with both. SP hell is almost serene, really...