Alright. I'm running with the stock launcher from Mojang, so it's not anything to do with that ( Hopefully ).
CPU - Intel Pentium G3258 OC'd a bit
GPU - Nvidia GTX 770 Also OC'd a bit
RAM - 4GBs at 1600Mhz
Display Drivers - 220.127.116.1188 according to DXDIAG, 347.88 according to Nvidia control panel. Should be the latest.
And I am using only the one monitor, unfortunately.
As far as Forge goes, I'm running with 18.104.22.1684. I'll try it with 22.214.171.1241 and check back shortly.
UPDATE: So here I was, about to post that updating Forge hadn't worked, when I thought, "Oh, maybe a copy of the game output would be useful." I opened up the launcher, changed the settings to leave the launcher stay open after the game launched, and hit play. Lo and behold, no problems. No lava and/or water replacing numbers. World loaded up normally, and shaders appeared. Didn't change anything other than the settings in the launcher, and before that, only the update to forge that had previously done nothing.
TL;DR: It works now, with no explanation. Sorry for any trouble, and thanks for all the help!