Optimal amount of brine for a pork butt

[JimD]

I know this is a very simplistic question but in trying to put together a recipe I need help on getting my salt levels right. I am tinkering with a recipe which is a roast pork from Ecuador. I am going to smoke it for pulled pork instead of roasting.

The specifics are:
5 Pounds Pork butt
8 cloves garlic
1.5 tsp black pepper
2 tsp ground Annato
1.5 tsp cumin
2 Cups pilsner beer
? Salt

I know that my liquid amount seems low but I will be packing it in a vacuum bag so contact should be good. I have two days for the marinade to sit and was wondering if anyone has an idea for the amount of salt that I should use. The original recipe would only use 1.5 tsp and that would be VERY bland I think.

Any ideas would be great, Thanks.