Okay. I have a tiny bit of semi-related experience with this. Background is that I live and work in Spain half-time. I'm in and out of my company's Spain HQ with a degree of frequency that while I'm not there permanently, I know some of the folks that *are* and have made friends with them when I decide to stroll into the office to be on the office network or get free office supplies or whatever to take home.

Now, Spaniards routinely refer to each other as "guapo" (handsome) or other terms of endearment that, in English, could be misconstrued as interest, when just casually talking with each other. One of my best, non-sexual (we've never had "relations" and doing so would be like trying to hook up with my sister) gay friends always calls me guapo, but also calls his little brother guapo, and his straight friends guapo. So it's not uncommon in Spanish society - straight or gay.

However...I've never heard anyone say "Amorcito" or "Mi amor" - which would be the Spanish equivalents - unless you're a parent speaking to a child or a BF/GF to their partner. I could be wrong as I'm not Spanish, though. Even stranger is that your Spanish colleague is specifically using French. Does he think YOU are French so he's maybe trying to bridge the perceived language barrier? I think this whole cross-language aspect adds a bit of uncertainty to it.

I probably haven't helped at all, but I think there's potentiality... Maybe start responding with "Amorcito" and see how he responds? Or "Guapo"? Since you're just returning the favor, either he'll be like "WTF?" and get the point, or he'll take the hint that you're also DTF or date or whatever and it'll progress.