Can you please help me in choosing or making the best quality food for my dog?

[Luv1self]

I want to choose a HIGH QUALITY DIET for my dog. I'm willing to buy or make the food myself and cost is not an issue; I simply want the best possible diet for my best friend. I am confused by the information on the net, much of which is contradictory. One source makes a recommendation and another discounts it.

I am looking for experienced and highly knowledgable opinions! Thanks!

Considerations:
--5 y.o., active lhasa.

--Generally healthy, but sometimes has mucousy stool which I haven't correlated to a source. He also sneezes a lot and has runny nose and eyes. Doc says this is allergy, however I suspect it is a result of his smashed in muzzle. No allergy meds have helped and present in every season.

--He is a very picky eater; historically I have mixed in a bit of cooked ground beef or turkey or broth with his kibble.

--Also need recommendation for a good quality treat that I can buy or make. He likes cruncy biscuits but most sources say flour, wheat, etc is bad.