Good Thread and good important points so far.
For the "no option to switch back to standard values" while tuning, I found out a little trick which doesn't compensate the lack of a button for it but helps sometimes:
If a given car had standard parts installed before, you can select that standard part and switch back to your let's say bad custom suspension to get it's original values back.
As far as I know, this works for every parts, where standard part is still an option.
If that way to get some standard values back was described already, nevermind.
My contribution to the list would be, that in online mode, the columns "one make" and "one class" are useless, because when you set it, no other restrictions can be set anymore like pp value, tires, weight etc.
Useless for now, seems to me like a placeholder for future updates (I hope so, at least).
edit: one mor thing: PD switched the damper settings for extension and compression vice versa. It's ok for me, but reading tuning sheets here right now is confusing, especially when only numbers are written down one after the other (like, is it compression or extension what I have to set!?).