Hello:
I know what you are feeling. I went out with a "boy" (man..36 years!!) but he behave like a teenager and gave me the same mixed messages like your friend.. but believe me at the end people don´t change that much. He was a great guy and changed almost for year and a half, we had a great time but I think he was not a keeper, you know.
If this guy already told you not expect too much, so what are you doing there? if you want an open relationship or something like that this must be the boy, but if you want something serious... get out of there... a lot of guys are looking for real love...
Good luck!!