I was wondering if i was feeding my puppy to much. He's 15 weeks old and all he wants to do is eat any thing and everything (cats food, other dogs food, and even trash). I give him little over 3 cups a day spread out between 6 meals. we walk 1-3 miles in the morning and 1/2 - 2 mile in the morning.

3 cups is definitely on the high end of what he needs, but that's pretty normal.  

Also, why do you feed him six times a day?  This is very unusual and is not a pace that is going to be easy to keep up ongoing.  Also, in line with your other thread about him being obsessed with eating cat food, it seems like he has very little to no structure around food because it is so readily available all the time, given to him so often, and he expects it now all the time.  

You aren't doing yourself any favors with your goal of teaching him boundaries, and there really is no reason for him to have such regular, constant access to food all day long.  

2 structured meals a day away from the cat food and ideally from  your hand would be best.  I get the sense he needs boundaries and structure so I would do some version of Nothing In Life Is Free training with him where his meals are given as a reward for doing something that you've asked him to and patiently waiting for your approval.  Eye contact and calmness are key here.  

Sounds like he has a free for all with food and you need to tighten things up with his routines and with some boundaries.

He's also still a growing puppy and you want to be very careful with that much daily exercise, especially if it's on concrete.

You can cut that # of hours if on concrete or make sure you're on soft surfaces like sports fields or grass. His joints are still growing and expanding and are sensitive to too much stress from over exercising.

You want to be moderate with the time, pace, and hard surface exposure.