Hot water helps break down the venom as well, yes. However that isnt practical to keep in your stand and timing is eveything. The sooner you get vinigar or hot water on the effected area the less pain you will ultimately be in. unfortunately I am speaking from a place of authority on this. I prefer to house my charges in ideal environments, not "perfectly adequate" while I don't have any dwarf at the moment when I did I had a harem in a 75 the alpha male was easily over 6" almost 7" just a hair shorter than the length of my hand. I might go back to keeping Dendrochirus some time as a lot of the other Scorpaenidae fish I want either don't get large enough or are not available in larger sizes at purchase to go on my venom tank. Full grown Volitan and Scorpaena Plumieri are just too aggressive for the small Inimicus sp. I can find in the trade.
Sounds like a nice tank! How many were in the harem? Also, got any pics?