I understand that you don’t want to marry or living with a possible romantic partner. There are many circumstances by which someone decided against giving this step.
I myself, if my relationship with my partner doesn’t work. I’m not ready to be with anybody else. For our age, our circumstances, avoid headaches, etc.
Luckily the times where a woman or a man were seem as spinsters and oddly if they didn’t live with a spouse passed away.

Said that, it’s understanding you have your needs, as everybody have, as a person, as a woman. But surely, what people who wrote here in the thread, and I think I’m not gonna be very wrong, are worried about the way you are making now decisions only with your heart. It’s very human so please, don’t feel judged.
This is the hard part to do and to learn here, in my opinion. Make the impossible in these situation to allowed your head also be cool and help to make the right decision. Especially for you.

Of course, we can’t tell you for sure whether any of these two men you have mentioned are or aren’t the right ones. We can only tell you from the clues we get.

Correct me if I’m wrong but I see disappointments behind your words in many of your replies in this thread, what it was not right for you before now you are able to put up with.
My question for you to wonder is if you truly are able to renounce to your own convictions and change them or you are telling this only out of pain.
I tell it because in relation to the first guy, you nearly give him the reason because of his prejudices about people with mental illness.
Now, this other guy, you seem to accept a situation of mistress that you didn’t accept in the past. And even you dare to have him as a professor, someone who is gonna tell you how to behave. As if he was the most appropriate person to do it.

Can I ask you something? In which context the other Muslim friend told you this friend was a bad apple?

Don’t feel judged, please. It’s up to a point normal that we don’t want you to give a step that can affect you if it depend on us giving you some insight.

Finally, do you know this last guy face to face? It has been already pointed out that there’s a big difference between knowing someone only from online contacts than when you know them also irl. This last, can give you a lot of information that I’m sure you are gonna catch.
In general, online things seem more intense because of the distance, because it’s easy to led us drive by words and what your own head make up about the other person. So, this is a difference to also consider.

You are being very opened here and this is good because it’s easy for others to have a big input when expressing their concerns and questions about the matter.
So, I think you are doing a brave and correct thing here. Take each response as a way to try to help you and of course, a personal opinion, without knowing all the circumstances you live in.