Welcome to the forum.
Responding only to the title of your question, before reading anything else: kissing does not transmit STDs. It doesn't matter how high risk your spa contact might be in terms of his or her sexual behavior. There is no risk, you do not need testing for anything, and you can safely continue sex with your regular partner(s). Unless there is a big surprise as I read the actual question, this opinion and advice will not change.
Now I have read it. Guess what? There is nothing to add to what I already said. In addition, hand-genital contact isn't a risk. As for oral herpes, in this context it doesn't count as an STD. I cannot say there was zero risk for it (from the kiss, not the hand job), but it is low enough that you can and should completely disregard it. By far the main health risk from kissing is catching a cold. From a health perspective, there is nothing in this event that requires it be mentioned to your wife.
Regards-- HHH, MD
Accept the reassurance you have been given and move on. That's all for this thread.