Need advice on additions to a kit

This is my 5th brew, all my kits have been brewers best which have come great. I am going to do the brewers best russian imperial stout. I was looking to make some additions to the kit recipe.
the kit
6.6lb dark lme
2lb dark dme
8 oz maltodextrin
8 oz crystal 60 l
8 oz roasted barley
8 oz black patent
1 oz columbus bittering
1/2 oz palisades aroma
yeast safale s-04
I want to add some chocolate malt briesse 6 row I need some help.
I have one pound but need some advice on how much to add and how long of a steep time. I dont want a overpowering chocolate flavor I am looking for subtle notes. I was just going to add 6 ounces to my specialty grain bag (good or bad idea)
I was also thinking about adding some coffee beans and vanilla to my secondary any opinions are welcome this is my first time I am looking to deviate form the given recipe.

well i would say add 0.25 lb of the chocolate malt and steep as normal... as far as the coffee goes i would add it at bottling time. grind up half a pound the night before and let them soak a half gallon of water over night in the fridge. then use a coffee filter and pour the coffee into the bucket.