coworker?

Hello everyone, I need some advice/perspective.

I have known this coworker for a little over a year. He is 50 and I am 30 and we work in different departments but often have to work together. He is good friends with my supervisor (a male) so throughout the year he would periodically come to our department to see him and chat. Whenever my supervisor wasn't there he would come and chat with me instead. We share a lot of the same anxieties so he referred me to his psychologist, but I never went-initially/

Fast forward to this summer, my husband tells me he wants a divorce. I am distraught and a few days later I email my coworker asking for the psychologist's name again. I have been seeing that psychologist for awhile now and he is fantastic.

My coworker, who is married, has started talking to me more, being very very open about his relationship, his unhappiness, his wife's unhappiness, etc. He has been trying to build my self-confidence, telling me not to go back to my husband, telling me I deserve better. He has a few times commented on me looking nice, noticing when I got highlights added in my hair, etc. He checks in with me on weekends to make sure I'm doing ok -- all of this is what I viewed as nice and someone who is genuinely concerned for me...but there are a few instances that seem a little off to me.

- he has my cell phone number and had used it in the past to call about work related things, and then when my marriage crumbled called me twice to see how I was doing. We were at a training recently and he was sitting next to me and had his phone on the table, he went to type in my name to text me something but my name wouldn't come up, so he asked me to put in my number again. It is not a new phone, so he must have deleted it at some point.

- He will text me sometimes, but email me others. For example, on Friday he emailed me at 10:30pm a motivational message...but he could have just texted it. He seems to text only during hours where he may still be away from home and email when he is home. Sometimes those emails turn into back and forth conversations as if we had been texting anyway.

- I was having a rough day a few weeks ago and I was staying late, he came to my office and stayed with me for 2 hours after work just talking. He told me he would take me to lunch the next day (we have previously only been out once for lunch and it was kind of awkward), told me not to bring my lunch, and then the next morning came to see me and bailed on our lunch plans.

-He called me to his office (not unusual since our work is related) and asked me a silly question about work then kept asking me to stay for "just another minute" but we really didn't even talk about anything, he was showing me periodically what he does...which really does not impact my work.

-We were discussing someone else's affair and he went on and on about how people have affairs, how could they lie. He said even if he got divorced he doesn't know how he could ever find someone else because that person would need to know his child comes first. He has brought this up numerous times after that day and has said no matter how hot a woman was, it wouldn't be worth ruining his marriage and starting over. But then in the same breath he says he is not happy with his wife and she has expressed the same.

- My therapist (the same one he goes to) seems to ask a lot about him during our sessions. At one point he flat out asked what the relationship was between the two of us. Then another time he made a comment about him doing extraordinary things for people he cares for but that there was no ulterior motive there.

-Recently he's been around more, calling me to his office to just talk, and we have been out to lunch now three times - he paid all times.

-He keeps telling me I am so lucky because now since my divorce the whole world has opened up to me and I have so many possibilities.

I enjoy his company and it feels nice to have someone looking out for me during this very difficult time in my life. However, I love my husband and wish we could reconcile. If this coworker is simply genuinely concerned, then great. But, if his actions appear to say otherwise then I need to set up some boundaries as I am not interested in ruining a marriage. At the same time, I don't want to assume something more is there when it's not and make the situation even more awkward and complicated. Any perspectives would be much appreciated! Thanks!