By day's end - for the last few months - inside of my mouth has sprouted little, white pustule-covered sores and neck glands swell. by next morning, ?

Hard to say: Pustule implies pus or infection. If it is associated with swelling of neck "glands" this may be sialadentis: inflammation of one of your submandibular glands. I presume the "pustules" are under the tongue? Either way... What you are describing is not normal, i would see your local ent.

Sicca syndrome: It is best to have these sores looked at to be sure they don't represent a generalized manifestation of another disorder. Many times if we mouth breath in dry air the taste buds and the lining of the mouth will dry out causing these swellings. Similarly the saliva glands will dry and as a result they swell. Biotene spray (otc) can really help as can increased hydration.