Just to give you some honest perspective - me and my husband have the same age gap. He also has exes in another country, some of which he still talks sometimes (which is fine for me). One of them actually hosted him when he lost him home and job. We made the joint decision to pay this particular ex a sum of money we found fit.

Your relationship CAN work. The age gap will make it harder, but not impossible. In our case, day to day, it's not a big deal. Your partner needs to understand that you trail behind him in maturity, and will be doing so for a long time. You are younger, there is no shame in that. Your partner also needs to check all other boxes any partner should - open, honest, communicates with you and makes you a priority. If this sounds like your partner sit him down and ask him to please sever ties with this woman. That's your right.