"My serious question is this - now that the Republicans control the White House, Congress and the DOJ and that apparently Trump's supporters don't care what Trump does, just what happens if no one that has the ability to do something about this, chooses not do so?"

First, our government does have the ability to do something about this. Here is what I see as the major obstacle and why this process may not move at the speed it should.

Both Republicans and Democrats want to see how far Trump can go and what precedents (always the key word) he can set. Why? Because they all want to see how far they can go and still be above the law. Trump is the perfect test case because he is both ignorant of the law and procedure. He literally has no clue what he is doing so right now all of the Republican behavior points to one thing, they are testing how far they can push this and all of it will end up on Trump anyway. So, basically they have nothing to lose...except Trump and I don't think there are many people that give a damn about that. I think most of these Republicans would prefer Pence anyway. It has become pretty clear Trump has no idea how he is being used and who he is being used by. The Russians are having a blast with him and he is totally clueless about it. That stunt Putin just got away with getting his spymasters into the oval office with a Russian camera crew the day after he fired Comey was so ridiculous I can't even believe Trump was dumb enough to allow that one. And to top it off he gave them classified information he was not supposed to share while they were there...you can't even make this stuff up. This is why the Russians are laughing in all the photos.

And the White House response was priceless..."They tricked us."

Trump and his staff lie about 1000 times a day and in the one instance they probably should have they just said "They tricked us."

Wow, this is the dumbest group of people ever to control the White House. You would think that all the people that screamed about Clinton's private server would be screaming about the fact that Trump idiotically invited Russian spies into the oval office, with their photographer and gave them...just freaking gave them...classified info he was not supposed to share...the day after firing the man in charge of the Russia investigation. Trump is the definition of dumb.

"What if Congress refuses to investigate this? What if the DOJ chooses to ignore all this?"

Not likely that happens. Trump continues to do things that are getting him into hot water with both the IC and FBI. DOJ, even though that utter clown Sessions is AG will not be able to ignore this...mainly because in case anyone has missed it since Trump took over the White House is leakier than the Titanic. They are and have been in cover-up mode for some time but that is what tends to sink the ship.

Trump literally buried himself with his tweet threatening Comey with "tapes" and it is now known Trump has been recording all his conversations as president. What the idiot does not know it seems is those "tapes" since they were made by the president DO NOT BELONG TO HIM, they are government property and belong to we the people. If he destroys them that is now a crime. They are now subject to subpoena and so he has to produce them. Obviously he does not understand what happened to Nixon.