The first thing I will do if she does not answer my text, and I know (just by the way she was texting me before) that she definitely received it by now, is send a text like this, “K sounds good lol” or even one like this, “All right hun that sounds Awesome lol.” Both of these make light of the fact that she didn’t answer you. They are short and sweet. They do not blow it out of proportion that she ignored you. Instead, they make a joke out of it, and they usually work to get a response.
After all, no one knows your marriage or your spouse better than you do. Texting affairs are the gateway to emotional and physical affairs. Of the infidelity cases I've dealt with in the past several years, the vast majority started out as "innocent" texting between opposite-sex friends or acquaintances. You are not over-reacting by insisting that a spouse end a texting relationship that you feel in your heart is undermining your marriage, and you are not over-reacting by treating it as a form of infidelity.
Minor things like punctuation are not as important as the spelling itself. If you’re trying to “speak” a certain way and you want to emphasize something, it’s okay to use three or four exclamation points. If she doesn’t use any punctuation at the end of her sentences, then you don’t really have to use it either. It’s not really a factor at all. At the end of the day, it really all comes down to the way she texts and the way you mirror that.
Referring to someone you just met as “hun/sweetheart” seems borderline creepy to me. It’s too superficial. If I received this reference towards me in a text before even a second date, I would not answer, or if I answered I’d let the guy know “thanks but no thanks”. Perhaps that’s just me. Instead, in the first text you can just refer to me by my name. Subsequently, you don’t really need to address me directly, just say “Hey” then continue on with your text. After a couple of successful dates (meaning you were both smiling and/or laughing at times, and both seemed to enjoy the dates) the nicknames and cute references like “sweetheart” will feel more natural and fitting.
A lot of these one liners are really good for text messages, but you really need to do a lot more than just a one liner to set yourself apart from the rest. Remember, today’s dating world is fiercely competitive and guys are up against a lot of other guys competing for the same girl all because it’s so convenient to get in touch with one another. Online dating is just making the situation even worse, when anyone with a selfie can sign up and get spammed by hundreds of suitors in a few seconds. Keep these in reserve for after you get to know someone. The funnier ones especially: who doesn’t like to laugh?