Boned pork shoulder fridge life
I'd trust the butcher if he is recommended; perhaps check on him by asking safe cooking temperature? 145°F by the way, it's been revised since old days 160°F. He isn't talking about all pork, he's talking about the specific cut from a specific source, that's been handled in a specific way. 

Even if meat gets a smell, there are different smells and if it isn't sort of a fermented sour smell, it's good. Same for color.
Easiest way to deal with the situation is to marinate it wet or with a dry rub. I usually do this with most of my meats the day I purchase. Some thicker cuts, especially pork, can take 4-5 days to take the flavor. Salt, pepper, chilés, mustard and a host of other spices help as preservatives.

https://www.cdc.gov/foodsafety/fdoss/data/annual-summaries/2015-report-highlights.html

Single food categories associated with the most outbreaks:

Fish (34 outbreaks)
Chicken (22 outbreaks)
Pork (19 outbreaks)

Restaurants (469 outbreaks, 60% of outbreaks reporting a single location of preparation), specifically restaurants with sit-down dining (373, 48%), were the most commonly reported locations of food preparation.

There were 30 multistate outbreaks, including the following types of foods linked to them:
Vegetable row crops (4 outbreaks)
Seeded vegetables (3 outbreaks)
Grains, such as flour (2 outbreaks)
Herbs (2 outbreaks)
Mollusks (2 outbreaks)
What, no pork?

CDC reports salmonella in local sources as leading reason for illness from pork, but it's half as likely as getting it from vegetables.