I think my husband is cheating with his boss

Please let me know if you'd be suspicious too or is this just a big coincidence?

I've been with my husband for ten years, together for twelve. He's always called me his best friend and prioritized us until recently.

His priority switched to working out constantly. As in daily, and sometimes twice daily on the weekend. I have supported his health and fitness, but I did let him know that I found it upsetting that he schedules our life around workouts rather than workouts around our life. He wasn't responsive.

Then he overhauled his image, new hair, new glasses, new clothes. Don't get me wrong, I think he looks great, but considering what has followed I'm not sure this was self improvement for self improvements sake.

A few months ago he got promoted and started working closely with his (very attractive) female boss.

The background with his boss: she started a company with her husband, then apparently started sleeping with an employee. Her husband divorced her but they still run the company together. Okay, so my husband started working closely with her and all of a sudden is speaking about her in a completely different way. Once he was telling me about how accomplished and successful she is while trying to hide a smile. And another time when he was telling me that he thinks everybody else is all wrong about her, and he doesn't think she ever cheated, and that she's just the hardest worker...

Some other things:

When we married he wanted us to have the same passcode for all devices including our phones, we've stuck to it our whole marriage, but he changed the pass on his phone a few weeks ago.

A few days ago he also removed his YouTube from the tv. At that point I intentionally went and checked his other devices to see if he'd changed them, I could still access his tablet so I loaded his YouTube and looked at his 'watched videos'. I found he's been watching vids about attraction, flirting, 'signs that the crush is mutual' etc.

This weekend I was working a Saturday shift. When I got home he told me he didn't want dinner because he'd been to a restaurant. I assumed he meant a local place. But, after casually chatting I found out it was in the next city over and it was a fancier place. So I asked who he went with, he said he went alone. I'm suspicious at this point because he doesn't go to nice restaurants at all, let alone fancy ones by himself. So I casually pointed out it wasn't like him. He claimed he wanted to check it out before he took me there (another thing he never does), so I asked when he wanted to go together and thats when he started to back track saying he wasn't exactly planning anything, just whenever we're in that area. Which of course, is never.

Finally, and this is odd. But he's being more affectionate than ever, like stroking me if we sit on the couch together, but it's to the point I have to stop him because I'm going to get a friction burn, lol. Maybe I'm over thinking it but I'm wondering if its out of guilt.

If you were in my position, how would you approach this, what if I'm just being crazy?!