I don't buy the injury risk angle. For one, the 2015 injury was a collarbone. 7 pounds of pressure on any collarbone in the league-of any age-and the QB misses the same amount of time.
The transverse and compression fractures go in the same boat, unless there's reason to believe his skeleton is more fragile than it used to be. That's possible with certain medications, so I guess it's possible that that risk exists and is not being reported, but that's also something any NFL team would know in advance of offering a trade for him and a contract.
The chronic back condition he's had operations to address is an issue, and would be a factor in any consideration for him.
That said, they could easily structure a conditional trade for Tony if they wanted to. A conditional 4th next year, that escalates to a 1st or a 2nd if he either makes all-pro or the team wins a Superbowl, and de-escalates to a 6th or a 7th if he doesn't start at least 8 games. Something like that. It doesn't matter what the terms or the triggers of the trade are, you get the picture re: the structure.
If they're not moving him, it's because there aren't two teams that want him enough for one of them to lock it down. If that's the case, all you can do is hold on to him long enough that it's inconvenient for HOU, and then cut him loose in time for him to legitimately prepare for the season. Maybe you wait until the actual start of camp to make a point, but no longer than that. If that's how it goes down, the market was the market and you can't really blame anybody. The Texans were comfortable running the risk, and the payoff is it saved them a pick. Or Tony tires of not feeling the love and realizes it's not necessary for him to play this season, and he retires a Cowboy and the Texans are left trotting out Savage and everybody wins.