I find that sending your boats to cross the T works perfectly on almost every mission - exe, if the horizontal arrows are yours the the vertical ones are the enemy, this is what you should order your boats to do.
You generally start like this:
\/.....\/
/\...../\
Either side can be you. Order your ships to move to the side and ahead a little, so they end up like this:
\/.....\/
<-...<-
Thus, you have crossed the T. It works -
this link better displays why.
Try playing more defensively - when I first started I did a DD patrol and figured I could drive right through the middle of some corvettes with my fleet... I got slaughtered. Practice torp'ing form a distance and unless you're going to slaughter them - exe Hood vs. MTB - try not to get too close.
For the freighters, again: try playing more defensively and killing the freighters with your cannon from a distance.
