Don't over season the meat and don't overcook it.
Add in shrimp and cook just long enough to heat - you don't want to overcook them!
Continue microwaving the chocolate chips ten seconds at a time until they are melted and creamy; do not overcook or the chocolate will become grainy and unworkable.
Shrimp is actually very easy to cook, with the primary caveat being that you don't want to overcook it.
Take care not to overcook them as the flesh will become mushy.