Sorry this is so long.... My questions are in red at the bottom.

I purchased a 2001 A4 with the 1.8T and 120K miles on it. The turbo went south on me after owning it just 3 weeks. Would like some help in figuring out why it went bye bye. I am getting ready to put in the new one and want to make sure I understand this whole system before I hit GO.
I have been around hopped up VW air cooled and Corvair engines my whole life. My Father build Dune-Buggy’s and so did I fo many years. Have built many of both engines and scattered many of both engines…. I know engines but not all the current bells and whistles.
This Audi seemed to have more of a “whistle” to it than most other turbocharged cars I have been around, and it is all stock. I started noticing (mostly paying more attention) that it had a terrible “flat spot” or “turbo lag” right off the line. I mean SCARY bad, I made a few left hand turns that I normally make where you have to slug it and you get through just fine, not with this car. On one occasion the oncoming truck had to slow down for me. But once she hits about 3k RPM it comes to life then you have to pull her back a bit.
The “whistle” I mentioned was very loud in my opinion, more noticeably driving in town from light to light. Sometimes I would notice the “whistle” stop abruptly, like it was controlled by a switch. Anyway I was just starting to research (online) different diverter valves for it and was planning on testing the one on it. Last Friday however on my way to work she fell flat on her face and was blowing smoke out the tailpipe like steam locomotive.
I ended up trailering it home that evening and pulled the turbo out…. The turbine shaft was broke into 2 pieces and all the fins on both ends were all messed up too. First thing I noticed when I started was the wastegate control valve (T-shaped with a solenoid on it) had two of the three fittings broke off, so I would say the wastegate was probably not functioning for a while. I also pulled out all the plumbing up to the intake manifold, it all had a bunch of oil in it, even the intercooler. I am hoping that the combination of the long distance, oil and intercooler that most of the turbo debris was captured. It took several hours to clean out all the oil.
I cleaned up and tested the DV finding it does not seem to operate properly, when I push the piston up and plug the hole for the vacuum line it does NOT hold the piston, I even sucked on it and could hear the air bleeding through from inside the valve (boost side I think)
So with all this said my question is…… Did this turbo fail due to the wastegate not functioning and the DV not working?My plan right now is to replace everything that needs replacing, I already picked up a new turbo and wastegate control valve and about ready to order a new DV….. Have seen a lot of comments about using the 710N, is this a good idea?I am going to clean out the oil supply line to the turbo then put it all back together. I am going to replace the oil filter and dump in some 10w-30 (have it on hand) to start in up and run for 5 minutes then drain and re-replace the oil filter and then dump in the real oil, 5w-40 Synthetic. Am I missing anything? Thanks.