Get at least 200g of protein. After that, do whatever it takes to get your calories in. The only foods to avoid are foods that might lead to health issues such as trans fats. Other than that, get it in.
You're already using a solid, progression based training program, so you're good there.
I'll just restate something I posted on FB the other day "The key to getting big and strong is to eat enough to keep up with your training and train enough to keep up with your eating." They both work hand in hand. Eat your 3k cals a day, then train enough that you know for a fact that most of it will go to muscle. You'll be happy with the results.
By the way, I used to weigh 125 as well. In 3rd grade. I'm not making fun, in fact, I had the opposite problem with weight and had to loose quite a bit to get healthy.
Current PRs at 242- 495, 345, 585, 1425