English past simple pronunciation help

In past simple tense regular verbs generally have +ed added to the end, some consonants double up first and of course there are plenty of irregular verbs to throw you off! But despite the ending being the same there are 3 distinct pronunciations, one o the tools we use in class is the following;

FreD

BerT  

DavID

~Words that end with the following consonants.... B G L M N RV or Z are pronounced with like the end of FreD... 

eg: beggeD swimmeD RibbeD

~ words that end with the following consonants ..... F ( includes some Ph and GH sounds) K P S SH CH or TH are pronounced with a shorter clipped sound more like the T at the end of the name BerT

eg:

Liked (likT) skipped (skipT) watched (watchT) Laughed (laughT)

~ words which end in the following consonants T and D are pronounced with an ID sound 

eg: 

wetted (wettID) fitted (fittID) wedded (weddID) 

Hope that helps some of you out :)

Great that you put this out here for English learners.

Though I can't help but notice..

swimmeD - isn't it swam?

wetted - I always thought it's wet for past tense.. though when I searched, I also found wetted. Now I'm curious, when do you actually use which one? Is there any rule? This is something new for me.

Oh my goodness yes I was trying to think of a word ending in m slimmed 

You can use it narratively in English she wetted her forehead but generally we would say wet .