Complicated question (To me) Dealing with steersman and 500 mate

I will be taking the 18 day Apprentice Steersman course (
which includes the topics listed at Delgado’s site. What I need clarified is will this course also make me eligible for a 100 ton master? I currently have 300 days 225 of which are on tugs over 100GRT the rest are still over 50GRT.

Second, I am aiming for the 500 ton mate within the next year, to my understanding these courses are valid for 1 year after completion. Would completion of the steersman course reduce the number of modules I would have to test for if I were to attempt my 500 ton mate exam?

Finally, the number of questions I am informed can be drawn from for these test seems daunting at the least, any recommended guides or methods I should look at for this?

As a side note, my company does periodic offshore towing trips along with the harbor work we regularly do, I have spent about 50 days offshore between Texas/Louisiana and Mexico, sadly the tugs used are rated under 100GRT, when I get a letter of sea time can the international tonnage for these tugs be used instead of GRT?