Many Men basically are pussies, they are unable to tell adoring women to back off, it is against their nature. They don't confront, and they don't get rid of fawning women. It's great for their egos....
IME - 9 Y E A R S of the Ex GF.... South American crazy woman who literally knew the score, but refused to move on.
Story goes they were together for a few months, She left the UK, I met P a few weeks later. A year or so later, when he and I moved in together, she got Leukaemia, so he couldn't tell her then. Fair enough. She knew about me, we emailed once or twice, that turned out to be an utter novella, so I knocked that on the head. I was always pleasant to her if she rang for support, she was always Amor this and te amo that, but what could I do really? she really could have died. As it was she was infertile at 30-odd due to the treatment.
When she got better, she reverted to the cow of before, riding rough shod over my time on birthdays, christmas etc ringing him a second past midnight, knowing she'd interrupt a date, calling all night. Calling and talking to me and lying about what I'd said, done etc.
Then I got PG. P didn't tell her. Over the last 4 years he never rang her once, she rang and rang and rang until he answered. The system there is to prepay the call whether you make it or not, so he felt bad if he didn't answer cos he knew it would cost her heaps anyway.
We were thinking of moving to the US at one point. She got a job in the US, the visa and the flight was booked. Again she rang and rang and rang, told him this. He told her that the US was not viable and that we were going back to the UK. She didn't take the job in the US, she blew the visa, after literally waiting 6m for an appointment with the US embassy, and lord knows what other hoops she had to jump through to be cleared for the role.
He only told her we had DS last year, DS is 5 in December. I was happy he told her, and thought she would finally understand the softly softly way... she rang a few times mroe, he didn't answer.
I read him the riot act after I heard about the US thing, it is so clear that she is obsessed and unhinged. he literally has not given her any encouragement for 9 years, yet she was giving up everything on the basis of one snippet of conversation, actually told to her to get the message across to her that he is out of reach, as the US is extremely hard for citizens of that nation to enter.
When DH came over here, she rang a few more times, said he'd call her back but never did. Eventually she stopped ringing... for now.
I told you all this, cos it's not always the man being weak, it can be that she is obsessed too. dunno if that makes it easier or harder.
Men are also woefully naive when it comes to women sometimes too... oh she is only being nice, being friendly... they just can't see agendas sometimes.
Let the dust settle with his dad and then sit him down and explain that she has no place in your relationship, that you need him, and she needs to move on. Tell him that somehow he may be keeping false hopes raised and that is unfair on her and disrespectful to you. Tell him you know he is a good man, that he doesn't want to hurt her, but this is what needs to be done, gently but firmly.
Jeez, long! but 9 years of crazy is not easily condensed...
Be firm. You have that right.