Hi
@Impoftheyard and welcome to the forums.
First of all, the good news, that hba1c of 43 is quite a way from diabetic so there's a good chance you can reduce your levels without ever hitting official diabetes. And you've already bought a meter, so you can see what's happening to your sugar levels.
I'm going to give you my favourite link about T2 and low carb (assuming your prediabetes is a precursor of T2, if it's leading to T1 then there's not much you can do about it). Though this isn't the only way to treat T2, it's the most popular one on here.
JoKalsbeek's blog | Diabetes Forum • The Global Diabetes Community
As regards illness, it generally pushes sugar levels up, so your experience isn't totally surprising. The hypos sound a little strange, did you check the dexcom reading against a glucometer? It's normal for morning readings to be a little high, because your liver pumps out sugar in the morning (dawn phenomena).
As regards the continuing higher levels, I'm T1 so probably not the right person to comment, but it sounds like you were pretty sick so I'm not surprised that things are taking a while to settle. I hope you feel better soon.
Many of our posters are in the UK so asleep now, I expect you'll get more replies soon when they wake up.
Good luck.