Just FYI, the old-tech mechanical contact VR's can
sometimes 'go erratic' .... showing 'good' output for awhile then 'whacky' for awhile, and back again. Even if it 'tests good' I'd pull the cover and inspect for signs of worn/burned contacts, corrosion, etc and R&R if the visible evidence indicates.
Yes, a battery generates explosive gasses. An ignition source is required to ignite, often an arc at loose terminal connection when hit with the heavy starter load (the vented gasses ignite externally and that runs to the gasses in the confined battery headspace = battery explosion). Another reason to ensure that post connectors are always good-n-tight.
More unsolicited FYI ....
The solid state VR sold by Hoye is definitely a quick and easy and modern-tech (long lived) replacement.
The mechanical VR can still be found by google searching the (likely Hitachi) PN on your defunct VR (~$20 vs ~$70).
IF for whatever reason you need/want to replace
both the alternator
and the VR, it's very easy to install an
Internally Regulated (solid-state) Hitachi 35A alternator to do the job of both (eliminate the external VR completely) for ~$50 (or less with a widely available RockAuto discount code). That
assuming your 3110D / 3T84 uses the same alternator as the 336D / 3T84A-N. Let me know if you'd like the details on that swap/upgrade.