Dog food recos - high fiber/protein?

I’m looking to change dog foods but I’m stressed over what to pick. My dog is 4 years old, 15.5 lbs and is a chihuahua mix with like 10 other things.

He currently gets the Wellness Small Breed turkey & oatmeal kibble, which is just the same food I’ve been giving him since I adopted him 3+ years ago.

For a couple of years now I’ve been having to give him a half tablespoon of pumpkin each day too in order to keep his poop nice and solid; if I don’t give him his extra pumpkin, his poop is way too soft and then his anal glands don’t express and he has an itchy, irritated butt! I want to switch to something that just has the fiber he needs without me having to add to it.

He also does agility now and could use a little help building up muscle, so I was thinking I’d look for a higher protein food too. We’re not SUPER serious with the agility stuff though so it’s not the biggest priority; it’s more just for funsies.

I know nothing about dog nutrition so any recommendations would be appreciated! Except a raw food diet, I do not have time for all that :joy: