there is no such thing as a het for pastel
The worst vice is advice... though here's mine, lol.
I personally think 50% Possible Het males are useless. It's a coin toss whether he actually carries the gene or not. Taking six years just to prove out a possible het male seems to me to be a big waste of time. Buy a 100% Het female if you really want to do anything with him, like kavmon said. They only way to positively prove he's a het is to breed him to a Piebald.
http://www.geocities.com/bait4snake
Read about breeding projects.
Breeding him to a normal... after 50% Hets there really isn't a term except saying "this snake's father is a 50% Het and its mother is a normal". Unless a snake came from a definite het, be it from breeding a het to a het, or from breeding a het to a normal, it shouldn't be considered anything. I think 66% and 50% is as far as it should go (unless you're talking about breeding a double or triple hets, but that's for another topic).
Markers... well, the only marker I've heard of is for the original line of Bob Clark's Albino Ball Pythons. They have an intense orange where the "gold" part meets the belly. I've tried looking for markers on Piebalds but haven't really found anything universal.