Newbie here

[DeepFried]

Hi! I just started playing SHIII yesterday and to be frank i'm struggling with some of the elements of torpedo targeting... now I know there are guides around here and i've read a couple but there are still some things that confuse me no end, hope someone can help.

First i'm playing the vanilla patch 4 (i think) game on steam, I have checked all the realism boxes except map updates (when i'm less confused i'll probably turn this off too).

These are some of the issues that are confusing me:

1) AoB - I understand what it is and what it does but what I don't understand is how the notepad AoB setting interacts with the TDC nor how (or why) the periscope bearing has anything to do with it.
This lack of understanding is probably the reason that the last aft torpedo I fired went at a 90 degree tangent to the solution I thought I'd plotted

2) Where should I start with this game? Do I just jump straight into a career? Ideally I'd like some practice intercepting lone cargo ships and practice with firing solutions, I've just been practising in the academy torpedo training up to now.

3) What is the best angle to attack a ship from if you're following behind? I can nail them ok if I get ahead and lie in wait at a 90 degree tangent to their track (which takes ages to setup) but whenever I fire at them from alongside or behind my torpedoes either miss or seem to just bounce off!

4) Sonar, what are the basic rules for picking up and tracking ships by sonar? I often seem to find my sonar officer picking up ships miles away but refusing to detect a ship right in front of us.

5) And finally what mods do I want? I don't want to mod too heavily and I normally play games vanilla tbh but I want to enhance realism (and possibly graphics). I have an ATI card, a powerful computer and a widescreen monitor (is there anyway to get the game to go widescreen or change the resolution?)

Sorry for all the questions but any help appreciated!

Edit: I should probably say i've not played a sub or naval sim before so its all a bit new.