That sounds clearly over the line, to me. Intentionally violating limits to get a reaction -- ANY reaction -- is a bad partnership (of any sort -- bdsm or otherwise).

There are times I "go for the safeword," but ONLY when it's a mutually understood situation: "I'm going to tickle you until you say your safeword," where my sub knows what's going on and that she should be using it to let me know where those limits are...and in that sense, it can be useful (I'd actually suggest this for those first couple whippings or endurance sessions...build up very slowly with a clear understanding of "say when"). If your beau is intent upon finding your limits and hearing your safeword, that's how I suggest you go about it.

I would think randomly doing acts that scare/disturb ones sub leads to a sense of paranoia, not pleasure....