Just chuck in the whole pack - don't bother splitting it. I use 2 packs in every 5 gal brew up to 1050 anyway. You're more likely to get a thorough trouble free ferment, with nice unstressed yeast and no off flavours as a result.
Dry stout -Nottingham
Off dry - SO4, Windsor, etc
Hops - doesn't make much difference if you stay off the weird and wonderful ones. Classic UK varieties are fine. Stout character is about grain, roast malt flavours, and bitterness The thing is, you only want bitterness from the hops so late flavour additions are not desirable so all the hops go in at the start of the boil and as almost all the hop flavour and aroma gets boiled off in a 90 min boil, it doesn't therefore matter much which type you put in as long as you get the bitterness you want. Northdown, Challenger, Fuggles, Goldings, WGV, Brewer's Gold etc, - doesn't matter. Guinness use Northdown and Goldings afaik.
I fairly recently won a club Dry Stout competition with one that had Saaz in. Nobody noticed .

It's what I had in the freezer.