If you have oil all over your engine bay then finding the source would have been your best bet to know. There's really no reason any oil lines or connections should have been disconnected to install a downpipe. The oil light will be set off by pressure (lack thereof), not by temperature.
You definitely seemed overzealous to get the car on the road and tested, and that's probably a small part of your problem. Especially with a downpipe, you should have let the car idle for a few minutes to help reestablish your fuel trims. Driving it at 75% throttle in the first ten minutes isn't going to have helped either because your oil is not up to temperature and flowing easily. Finally, you should have been watching your AFR, oil temp, and cylinder ignition corrections to ensure everything was operating safely.
The electrical oddities, minus the sync update, is weird and should have warranted you finding a solution prior to leaving.
My guess is that you damaged a turbo oil line at some point and will be buying a new turbo and line, given the location of the mess. If so then your engine is most likely fine. Best of luck.
As for the FoST stuff, a lot of misinformation and disclaim in here. All of the tuners have been affected, and there are plenty that occurred on the stock tune as well. Many people say that they were in low load when it happened, so a lot of them are most likely LSPI. As for the knock sensors, they are ridiculously sensitive which is why they have actual incidences of false-knock, unlike the FiST.
Even the OTS tunes show negative corrections, so there are really no safe bets. The thread does look rather brutal, but keep in mind the fact that they sell approximately 2:1 or more in comparison to the FiST and have been produced an additional year. There are probably at least 20k more FoST's on the road than FiST's. There's a significantly larger pool from which to have failures occur. They have higher temperatures and pressures to deal with than we do.
With that being said, the FiST does seem significantly less prone to having issues from my perspective. My FoST has been a complete pain to tune, and I'm one of those that doesn't have the oil-pudding issues. Obviously time will tell because at this relative point in time I don't think that they had had any issues either.