Hello, I am Rafael. Thanks for asking your question - I'm here to support you. (Information posted here is not private or confidential but public).
I am very sorry to know about your situation.
This is obviously a very challenging and concerning situation. You are describing an adult person who has separated from wife -according to what he has told you- but after two years he remains having daily communication, emotional intimacy, sharing, and more, but he denies any form of sexual involvement. In reality most times scenarios like this, where spouses do not live together but do everything you say he does with her, do also keep an active sexual life, that's why your situation what got my attention.
The you said he uses the tax thing as the reason for them not to divorce. Again, this reason is not common at all as a valid one in real life, but most times a justification.
He doe not have little children to justify staying married, but he has no way to justify not having introduce m them to you. One more red flag! Never answers your calls when he is with her... and he gets very angry if you mention the topic. I am sorry but these concrete issues are not only red flags but concrete issues showing you this person has not been honest with you at all.
The you report you caught him spending a weekend with another woman. This is very serious. I am afriad you have been too passive enabling all this abusive and unacceptable situations. It is obvious to be he is not honest neither even respectful towards you. No doubt fidelity is not a reality there considering the scenario you depict here.
I am sorry but believe this is a very unhealthy and painful situation , but you need to face the whole reality if you want to start taking good care of yourself and life, unless, you truly think and feel it is worthy for you to keep a relationship like this, with all these issues-limitations because of the pros you experience with him. Only if you truly believe that and were willing to afford the present and future consequences from such approach, you could keep gong, sure you can. But if your core needs and expectations in life are much better than that, then please look for professional counseling support in order to move away from such an unhealthy relationship.
Does it make sense?
You're very welcome. I totally support you. Please take gentle care and consistent action.
(Please do not forget to rate support in order to close session).