You are infatuted, in love with him, and happy with the addictive cycle of texting, contact, the 'what ifs', the longing. I wouldn't be happy whatsoever if my husband had spent his time as a stay at home dad like this, basically besotted with another person. If you really wanted to throw yourself into your relationship with your husband, you would not see this guy because you can't see him without all this besotted crush stuff. Same if I get a crush at work, I don't indulge it further and text all the time!
It's also very fantasy-based at a difficult time in your life, I'm sure the reality of life together would be very different, but that's not the purpose this serves.
I think the key thing is you can't have told your husband how much you text and that you want to extend monogamy into loving others (but not having sex) otherwise he'd have called you on it.
It's up to you of course, but I would not be happy being second best while my husband skipped about in the local park having play relationships with others while I was out at work all day and I'm guessing yours wouldn't too.
And hiding behind the 'men and women can be friends' is just a bit cowardly, given I'm sure you'd like to be much more and that's what the whole texting/longing/blah is all about.
Sorry if this seems a bit harsh, I just think you are kidding yourself and I would be upset if someone did that to me. I would not be upset if my husband fancied someone else, flirted with them for 5 seconds or looked forward to seeing his friends, but once they started to replace me as the source of romantic interest and excitement I'd be extremely angry and consider it like an affair. I'd also find it insulting, as I'd be the second best boring one.