The video shows 10 deep throws to Wallace. I believe it's missing at least 6 other incomplete attempts.
Tannehill made 33 deep pass attempts down the right sideline, most of them presumably to Wallace since he lined up almost exclusively on the right. He was 7 of 33 on those deep attempts. 16 is too low a number so I don't think this video and your count provide the true sample size.
Tannehill also made 19 deep attempts down the left sideline and connected on 7. Tannehill was much better throwing deep to his left.
In the vid, Tanny has good protection
Not on every play.
Wallace wasn't wide open. He was bracketed. This should have never been thrown to begin with.
Slight underthrow but completed for a touchdown. Wallace was wide open.
This was not good protection but Tannehill stepped up in the pocket.
This was not good protection as the defensive tackle was pressuring Tannehill from his right. Pass was underthrown but complete.
Tannehill was hit as he threw, not great protection, and completed the deep pass to Wallace, but it was underthrown.
Good protection, pass underthrown. Tannehill seemed to be trying to guide the pass.
Good protection, pass underthrown. Not sure if it was ruled complete or incomplete. Looks like Wallace caught it and ball came out later. I noticed a mechanical flaw in Tannehill's motion on this attempt. More on that later.
Protection wasn't great but Tannehill did a nice job of stepping up. I think this was actually a perfect throw and it appears Wallace slowed down a bit, but I could see it considered a slight overthrow. Maybe Tannehill didn't set his feet well enough after stepping up and rushed the throw? Should have been 6.
This was just great coverage. The corner was playing way off at the snap. Why force it? Why not change the route to a comeback at the LOS?
Tannehill hit as he threw. Ball came out wobbly. Not good protection.
I don't see why Wallace couldn't have gone up for this one. It was slightly high, but a receiver with good hands goes up and get it. This is a flaw in Wallace's game. He doesn't fight for the ball, he doesn't attack the ball. He waits for it to land right in his breadbasket. It's a two way street. Location is important, but so is catch radius. Wallace's catch radius is lacking.
Back to my comment in #6, it seems as if Tannehill drops his hips a bit and keeps his shoulders parallel to the ground on this throw. This may be why he has some underthrows.
Typically, when you're throwing a deep touch pass, you want to maintain your hips level, rear you shoulders back to give the ball trajectory and step into the throw to guide it up the field.
By dropping his hips, he is actually taking air out of the ball and relying more on arm strength, a fatal mistake when trying to throw deep is relying on arm strength. Your hips, legs and shoulders are more important on a deep ball than your arm.
By the way, Andrew Luck had a similar issue coming out of college. He did not have a consistent, credible deep ball and he spent a whole offseason working on it. He would left his back leg on deep throws and take power out of it.
Contrary to what people say about either having it or not having it, these things can be worked on and it is up to Lazor and Tannehill to work on the mechanics and up to Tannehill and Wallace to put in the time to build chemistry.