Having worked through everything, the best I can do is 7900 and I doubt you can get any better than that. (Pretty sure you've made a mistake somewhere. Yes, not me. You. 90% sure you must have thought you could drop effect veiler in your own turn or something.)
Normal TGU. Special sangan with its effect.
Xyz into giga brilliant. Solemn judgment it.
Summon DAD.
Summon zephyros by returning dark armed dragon.
Summon abyss dweller. Detach zephyros.
Summon DAD again.
Summon BLS, banishing giga brilliant and sangan.
Fiendish chain maestro. Banish TGU with DAD to destroy it.
Destroy mirror force with DAD by banishing zephyros
BLS attacks tiras, deals 400.
BLS direct attacks for 3000.
DAD direct attacks for 2800.
Abyss direct attacks for 1700.
Total is 7900.
If you want to know the reasoning behind this being impossible:
Effect veiler is pointless as it can only be used in opponent's main phase. The inzektors are useless as the only way to get hornet to grave is by bouncing and summoning armageddon, meaning you can't normal an inzektor. This leaves TGU, BLS and DAD as the only usable cards, armageddon and zephyros aside. The only way to get 3 darks to grave is to use TGU for an Xyz summon and have it drop both of its materials somehow, and the only way to do that is to solemn it. The only light/dark Xyz choice is giga brilliant, a light, meaning the best course of action is to summon that and solemn it to end up with 3 darks and a light to grave. From there, you summon DAD, then to maximise damage you can Xyz with zephyros and arma then immediately detach. However, the rank 4 Xyz with the strongest attack that can just randomly detach available is abyss dweller, on a measly 1700. Then, you can DAD again, then BLS. 1 dark must be used for mirror force. Fiendish and the last DAD pop must be used on maestro, as you wouldn't be able to kill him in BP and you can only choose one of the two. From there, there are no more actions you can take besides all the attacking, which totals 7900.