First of all a party this size requires day-of help from people who are not in the wedding party; 2-3 people in the kitchen and at least 8-10 out front to set up, serve and clean up. Yes, even for buffet. None of these folks can attend the wedding, as they will be working to prepare during that time.

These items are out when people begin to arrive, as appetizers:
Chips- 1 pound per 12
dip- 1 pint per pound of chips
Cheese- 8-10 pounds per 100, some can be logs or spreads
crackers, 9 pounds
pepperoni, 12-15 pounds- you could sup some deli sliced ham or salami for part of this.
Add a fruit tray, see the fruit tray page, at least a deluxe tray for 100. You can substitute additional fruits if you don't want to use all the ones on the list.

Have a punch or lemonade bowl, at least 10 gallons, plus ice. Can have a second alcohol-based punch for a second choice, allow 1 quart per 5 adults.

Pulled pork
Meatballs
Need to add a vegetarian option; with 150 people there will be some. A dozen veggie sausages (Field Roast is a reliable brand) or Boca or Morningstar veggie patties.
Need baguettes or crusty rolls- some people will make sandwiches- 12 pounds per 100
Corn- 24 pounds per 100 (4 #10 cans per 100)
Roasted potatoes- 40 pounds per 100
Pasta salad- 6 pounds dry pasta per 100, or use any of the recipes for pasta salad for 100 on this site.
I would definitely add slaw since you have pulled pork, about 4 gallons total.

To be economical for the wedding cake, consider having a grooms cake and/or "kitchen cakes", sheet cakes in the wedding cake flavor, to allow for a smaller show cake.