This makes me so happy to hear, Wendy! thank you so much!

I’ve never reheated food in the crockpot like that, so I can’t be sure. I would add a little bit of chicken or beef stock to it, I think it will help it be rehydrated/not dry!

No, I unfortunately don’t! I don’t think this would turn out as well in a dutch oven as it does in the crockpot

This recipe is much better when made in the crockpot than the instant pot. I personally thing the instant pot dries everything out and I rarely use it for this reason.
You mentioned that you cooked this for 45 minutes, when it was only supposed to cook for about 33 minutes. That extra time could’ve been part of the reason why it was so tough. If you make it again I would not cook it for any additional time. 15 minutes doesn’t seem like much time to cook pork, but you have to remember it’s also cooking as the pressure cooker comes up to temp, and while the pressure naturally releases. The meat was probably tough because of how long it cooked for. 
Pork tenderloin is definitely not the same as a pork shoulder/butt and it’s much leaner so it will inherently be a little drier/tougher because of the lack of fat in it – but it should’ve easily shredded.
If you try this again, I wouldn’t cook it for the additional time and I’d try it in the slow cooker. This Slow Cooker Pulled Pork is another option!

The recipe says ‘Marinate pork in olive oil + spices overnight if possible in a ziploc bag, otherwise place tenderloins in crockpot and cover with oil/spice marinade.’