I have a pH meter ($50) and use it throughout the entire brew. I check and adjust my strike water, sparge water, and check the mash first runnings, and sparge runnings.
Welcome David. You'll fit right in, you'll find everybody from high dollar turn key brewerys to dirty old boot open fermenters here. With that much seat time, you may be quite the contributor.
I do know that yes, you can sugar carb in your keg, and it will do so better at room temp, however the amount based upon serving temp I'm not so sure. My guess would be to carb it as if the serving temp doesn't matter, but that is just a guess.
If your gravity is off, it will change the sweet:bitter ratio I believe. Overshoot gravity should be on the sweet side, undershoot it and it should be more bitter. I could be wrong.
I’d top it off to try and hit the gravity so you will know the flavor that the recipe should produce.
I liked Ozark. Also, Dead to Me and Santa Clarita Diet. I've been wanting to watch Handmaids Tale but since it's outside season, it'll have to wait for inside season.