Help finishing a Baltic Porter recipe

[Thomsen1287]

I'm trying to finish a Baltic porter recipe,

I know that I want to use

4lbs of munich
1/2 lb of choc. Malt
1/2 lb of CaraBohemian
1/4 lb of Black patent

I'm thinking of using 4lbs of pale malt dme to round it out.

So first question is is that enough or too much dme

Second Im thinking about 2.5 oz of saaz all at 60 mins

Would also like suggestions on yeast as this will be my first lagering effort

Thank you!