Interesting stuff.
my earlier post points out why I think the warlock is out-of-bounds.
To address the fighting style, I like the idea but it combines with sentinel and polearm master to create a scenario where you very likely NEVER get within 5' of the fighter, much less are allowed to pass within 10' of him. Making such a fighter able to easily hold a 25' area of the board while, with kiting, taking very little if any damage.
There is no PC combo that can't be overcome by a competent DM. Instead of declaring the combo OP, make sure that your encounters are designed such that the combo only shines when the DM allows it.
How do you curtail TF cheese? High AC ranged units and creatures with teleportation abilities or combats in wide open areas.
How do you limit QCF? Make sure that all of your ranged combat takes place at mid-to-long range.
Undying Light? Throw lots of creatures with radiant and fire resistance.
As you can see, there's a counter that pairs with every cheese. It seems like every other UA article spawns a cheese & whine party...
Given Polemaster and Sentinel are already in the game the burden is on Tunnel Fighter to make sure that it doesn't allow for this overpowered combo to be created.