How to start end-game?

[Taika]

I'm getting close to starting end game too, I have a question. I see that
You can also get a wep from Titan HM does
This mean that his wep drop is even better than Garuda's?

Yes, but Titan is also the last step of the relic quest, which means that when you kill Titan, you don't need that weapon anymore (at least for that job).

When you say resets..., does that mean the 300 you have set to zero? I'm no where near end game, but merely curious.

They mean you can get up to 300 tomestones per week, and the limit resets on Monday at JP midnight. You don't lose the tomestones you had, you just can't get more than 300 per week (that's 8 AK runs).