What if Terry was the one who had Patton blown up

it was probably not Rusty so I think there will be a Twist, but Terry would not profit from his death in any way IMO. For him and his crew any disruption of the old order would mean a loss in their 'extra income'. A war in hells Kitchen would endanger their scheme.
Whoever killed Patton probably wants to takeover his empire or at least wants a piece of the cake. Now that he is dead his chosen heirs will probably not honor the agreement, become greedy and start a thug war to gain power.

I want it to be Ritchie. He was the one who was talking about killing Joe if he couldn't kill Rusty. Plus a lot is made about his being a loose cannon, a dangerous hot-head, and yet the last we see of him is fleeing into the house of his dead friend's fiancee.

I wish it had been revealed or even hinted that he did it in the last episode. It would make a lot of sense given his nature, his apparent abilities, and it would make a lot of story sense given Rusty's fear of being next on the hit list.

The twist would have been was that it was his grand daughter who was upset that he was giving away the family business