But, he wants to create the strong perception in Trump's mind that he does in the hopes that Trump just resigns or capitulates in order to avoid impeachment and being disgraced.

Think of it like chess. Mueller is taking key pieces after key pieces with the hopes that the player resigns.

I don't think it's Mueller's intent to force Trump to either resign or face impeachment. Both of those scenarios are political outcomes which takes that into Ken Starr territory.

I do agree that Mueller is working his way up the food chain. But that's where it's taking him.

I don't think Mueller would bluff that his hand is strong, I think he'd likely down play the strength if his hand so Trump won't panic and remove him somehow. His hand is likely much stronger than it appears.

flynn can easily enough tell mueller what he knows, but it can take longer to compile all the evidence.

if all mueller has is flynn willing to testify but no other witnesses or evidence to back it up, that's not a very solid case against donnie.

but if flynn can hand over diaries or emails or point to staffers or other witnesses, that helps build the case but takes longer for mueller to process, especially if it involves trying to flip more witnesses.

the "minor" details could be quite involved.

When will he testify? How often and when?

Mueller has Flynn's testimony and proffer already and can use this if Flynn tries to back out. This means that Trump cannot really pardon Flynn because Flynn will still have to testify and the proffer will be used if Flynn tries to change his testimony

There are lot of people he can indict or flip before he gets to Trump. He can go one at a time, as he has been, or go after a bunch at once. I suspect he will go one by one, try to get as many flips as he can then take down Trump last with overwhelming evidence.