I think the reason you may be getting confused with your own readings is because you are focusing on the work relationship as well as the personal one.
In my experience older men are generally flirty with the younger women, and it’s easy to get caught up in that.
These are the thing you should take into consideration before you decide anything.
He is living with another woman, so you have to tread carefully there.
Just because he says things aren’t good on the home front doesn’t mean that is always the case, so be careful with that as well. (This could also be connected to that warning that you got of an affair.)
As Watergirl18 has pointed out: He says he doesn’t believe love lasts, which could get you hurt in the end. (That shows you right there that even if you do want to get into a relationship with this man that it won’t last. He is actually expecting the love to fade after a few years. Why would you want to set yourself up for that?)
If you tell him how you feel and he doesn’t reciprocate then you will have to deal with the awkwardness of working with him after that, that can be hurtful all on its own.
My advice, if you still want to see what is there, whether he is being genuine or not would be…
Do what PisceanHealer suggested. Take it slow and have patience. Get to know him as much as you can before you decide to get into or go for a relationship with him. This way, you will know where things stand with him and there is less risk of you getting hurt.
It would also help if you wait until you aren’t working with him. That way if you two keep getting thrown together things will be easier to deal with and the business relationship doesn’t stand in the way.
Just be careful. Good luck.