Descaling: Miele CM5200 & other owner suggestions

Hi all. I have just become an owner of a nice Miele CM5200. I am guessing this unit is circa 2008-2012 from my research. I purchased it very reasonably, knowing if it didn't work, no big loss.

The unit was not abused and used little in the past 5 years. The owner knew little about it and had no idea it required descaling or brew head cleaning. The exterior was very nice with no visible damage.

Once I got it home, I opened the side panel and noticed how dirty the brew head was. I spend a few hours cleaning it and running it through a descaling process. However, I didn't have any tablets. It hung up at 3 minutes because I have since learned you MUST start with .5L of water.

I also went into the maintenance log and noticed it has around 9100 cycles of drinks through it. Can anyone comment on this being a lot or little? I have seen videos of this machine being tested up to 50,000 brew cycles in its development.

I have no error codes and it does seem to operate just fine for now.

Now to my questions:
1) Miele STRONGLY recommends using their descaling tablets. However, there are many generic brands available for about 1/4 the price. Is it necessary to use Miele? Are they any different or better than generic? Could I just use a 50% solution of vinegar?
2) Should I open the entire case and perform some "basic" routine service of specific gaskets or "O" rings?
3) Any need to take the brew head apart?
4) Any other suggestions would be appreciated.

Lastly, the only broken part I have noticed is the nipple on the "Central Spout with the Integrated Cappuccinatore". See picture. I have not yet been able to locate one. Any suggestions new or used would be helpful.