Sick Puppy - Can PET Plus Help?

We have been the happy parents of our Border Terrier since February 2020. He came to us on a poor kibble diet, so I switched him to a '"better" kibble and bits of other stuff. Until I saw sense and went on to raw (in October 2020) as my previous dog was years before.

However I'm now using pre-made BARF rather than DIY. He has always been on the smaller side, but the life and soul of the party, seemingly happy and healthy. Had the usual puppy vaccinations and initial wormer and flea treatment. Then switched to Milbemax and now gone natural.

He is a scavenger and not a discerning diner. An eco-friendly feeder has now slowed his eating down. I have just ordered a worm count kit to get a baseline count, then plan to add a natural wormer (VermX or alike) on top of helpful feeding (organic pumpkin seeds, Furry Dog treats, grated carrot etc). No flea treatment is currently used (looking at options for that).

Three weeks ago we think he ate something on a woodland off-lead walk and was rather poorly. Very sick at first, then at the other end. After worrying advice from the traditional vet, I got a mix from my homeopathic vet to support his liver, kidney and pancreas. He is back to normal on the whole (took 12 days) with support from careful raw diet with added bone broth and the remedy.

He needs to gain another half kilo, which I am looking into with his food.

I wanted to add a soil based pro/prebiotic but now think enzymes may benefit him too. Do you think your product will cover the bases he needs? Any advise on his weight too? Thank you.