Since retiring over 10 years ago and had "time on my hands" I've experienced many episodes of anxiety symptoms. I have had a number of GP visits and been referred twice to hospital for a procedure where a probe is inserted into the nose and down throat. Quite a weird sensation. Both times the result was negative ( thankfully) and been told that my symtoms are all anxiety related. I've no idea what I could be anxious about but these sessions sometimes last for weeks, even months before mysteriously subsiding. I've had the lump in the throat sensation, the feeling of a swollen & tingling tongue, stiffness in my neck, aching glands....you name it & I bet I've had it. Its a catch 22 situation not knowing why and the wondering only makes it worse. Hope my experience puts your mind at ease. Take things easy, try not to "over think" things
You should talk to them both (separately and in private) and ask what's going on. If your husband doesn't stop then he is stepping over the line and you need to put your foot down. If it is really bad they would do it in secret though so be aware of this and ask his ex if she notices it as well.
Wow I think you should trust your insticts, they are usually right. Can you talk to her also and tell her, I know you love your dad and your dad loves you but somethings are inappropriate??? Tell your husband that you are his wife and that he has been with you for a long time and because of that he should trust what you are telling him. Well hope this helps. Good luck.