1) Missing -> 125 == about half way between exits 124 & 127.
3) NEW -> 219 == Probably center it @ Robert S. Light Boulevard based on the BGS's for the exit.
4) NEW -> 321 Callan Ranch Road (shown as Telephone Rd in OSM)
5) [I-35Gai] NEW -> 503 == About .8 miles from 504, enough IMO to justify a separate point.
https://github.com/TravelMapping/HighwayData/pull/22452) 217 should probably be moved a tad to the south and centered on Kyle Crossing.
This one, I'm of a bit of a different mind on. TX interchanges have their own unique wibble & wobble, often being spread out for some distance over the frontage road system. As you've no doubt seen. While I'd normally go with where the major crossroad is located, here I think may be more worthwhile to center the point on RM967, allowing a graph connection for when the RM roads are eventually drafted. I think there are some other examples of this around Texas, though I'm hard pressed to come up with any off the top of my head. It's been a while. To be fair though, what I have a more clear memory of is a case of multiple bridges/crossroads over the freeway, one of such being the FM road. I'm less sure about a case like this where the other highway just ends at the frontage road.
OTOH, I've ended routes
at the frontage road in some cases, though I've
not always been consistent in this approach. The way TX works, we're bound to have some routes without graph connections at the end; I recently saved
a list of examples from the usatxl system (and there may be more examples from other systems I didn't root out.)