Macy - I've just checked the JWB website for quantity - guidelines for puppies and it looks as though he needs a bit more food.
I'd expect him to reach about 32kgs as an adult, so at nearly 3 months old he could need as much as 405g per day!
TBH, that sounds like a mammoth amount for a tiny pup - but their food requirements soar in the first few months because they grow so much.
How many meals a day is he having? I'd manage the necessary increase in quantity over 4 small meals a day I think - it'd make the change easier to manage for him.
Are you taking him out and about with you? Obviously, he can't touch the floor, but it's really important to carry him about to get used to things - cars, busses, lorries, men in hats, men with sticks, screaming people, lots of people, motorbikes, fire engines, everything really. Sit on a bench with him on your lap for 5 mins and just watch stuff.
When they're tiny, they are pretty bullet proof and just accept everything you introduce them to. Socialisation is the most important thing you can do with a puppy - it will result in a calm and confident dog who has no fear.
The window for socialisation isn't massive - so my advice is get him out and about - I resort to a rucksack for mine when they get too heavy to carry!