Quick update: I went to two places today to get the battery and alternator checked...my local Autozone and a trusted independent mechanic. Both came up with the same result...alternator is good and the battery checked out okay but with a low charge. I drove the 4Runner around town for a couple of hours and did not see any more venting or odd behavior.
I'm not sure what to think now other than I will be swapping out the questionable battery for the Odyssey PC1500...just need to make a spacer.
2004 Land Cruiser -- OME/Slee Suspension | F/R ARB Lockers | 285/75-16 Nitto Terra Grappler | Slee Armor front, rear, sides and belly | Dual Battery | ARB Drawers