Yes I would try the X-blender if you are having trouble dialing in your wet signal (delay/verb). You could also install an effects loop as there are many nice ones out there. As for 'thickening' your tone here's what I would try:
1) bigger strings
2) lowering your tone controls
3) adding more gain with the FD2, then lowering the volume on the LP. The electronics on most Les Pauls are wired such that when you lower your volume things get a lot more mellow and thick sounding. Joe does this all the time.
4) like you said, there's sometimes no substitute for volume
5) perhaps try the 'FM' mode on the Fulldrive, this mode has more low end and less pronounced midrange than Vintage mode
6) If you are after the THICK tone, I've never tried anything thicker than the BK Butler Tube Driver. A close second would be the Xotic BB preamp. These two pedals are very thick and make even the thinnest guitars have meat! The Xotic BB is wayyyy more transparent and would work very well stacked with the Fulldrive I'm guessing. The BK Butler kind of takes over the signal chain and is less transparent than the BB.
'67 and '74 Fender Twin Reverbs, '74 Marshall 1987 lead mkII, Metro Superlead 100. Pedals from TC Electronic, Ibanez, Dunlop, BK Butler, Electro-Harmonix, Fulltone, Maestro/Gibson, Loopmaster switching, VoodooLab, Boss. Gibson and Fender guitars, Dimarzio pickups.