You are indeed correct on Houston being spread out.
Yes, the suburban areas are affluent, but like you mentioned with Glendale, that could dissuade people from making the trek; especially if the team is mediocre, which playing in Houston is almost a given.
One of the reasons I think the NHL finds Houston and Atlanta appealing is their desire to diversity the fan base. However they measure it, a few years ago a study deemed Houston the "Most diverse" city in the country. From my experience, this is true. I would imagine in that regard staying closer to town is a better idea.
I checked and Wells Fargo opened in '96, and Toyota Center in '03. Only a seven year difference, but on the other hand, I haven't seen complaints about other buildings in that age range.
I was kinda joking but about the Astrodome location, but it's actually a good idea. I have no idea why it's still standing, taking up valuable real estate. It's right by NRG Stadium, which has light rail, parking, and freeway access. NRG has hosted multiple Superbowls, Final Fours, etc.
There might be a temporary issue in March with the rodeo, but just send the Aeros on their West Coast swing while that's going on.
I'm maybe a bit biased on wanting the Astrodome demolished, from childhood trauma watching the Astros and Oliers snatch defeat from the jaws of victory in unfathomable ways.

But I do like the Philadelphia idea of having sports venues in one location, maximizing parking and public transportation since teams rarely play on the same day.
(That's a picture of the Astrodome in the shadow of NRG, that's not showing up.