it is tough going from SH3 to SH4.
" The periscope TDC stuff: what does the speed/track calculation button require when it says it doesn't have enough data? "
The speed estimation function requires two separate range calculations. The longer the time interval the more accurate (in theory). I believe that when your crew reports not enough data, they are asking for another range reading. Try to keep the range readings about 10 seconds apart.
"The position keeper: best to activate after a full initial set of data is in, or after the range/bearing is in?"
well there are some who never use the PK. Reference this lively thread
http://www.subsim.com/radioroom/showthread.php?t=133122
If I were to use it I would wait until I had a full set of data... If I ever used it.
"And now onto the bane of my current existence, the US TDC. <.< I wasn't laser-accurate in SH3, but here I am ridiculously bad."
Same here. I was actually pretty good at manual targeting in SH3 but I find the controls in SH4 awkward and slow to use.
Try Rockin's technique in the thread I give you. It is a pretty good technique that really helped my manual targeting in both SH4 and SH3.
"What does the red 'S' on the torpedoes panel that usually has a tooltip of 'poor' mean (can I guess that it's my solution?)?"
The red "S" is to tell you when the Ice Cream machine needs servicing. I can't seem to find any other use for it.
Good Hunting