<Sorry, I simply don't agree that there is such a thing as a "passive participle" in English. >

That's fine. In linguistics, there's continual disagreement over terms. That's a healthy thing, IMO.

<Neither "am" nor "loved" of themselves provide any passive meaning:>

Yes, I know. Many words have no specfic single meaning when on their own (e.g. blue). The words "loved" (verbal) and "loved" (adjectival) are seen as homonyms by many linguists. I suppose you also don't see the need for the term "passive be". Passive be requires (=selects) a passive participle complement.

<* For that matter, because "loved" is a regular "-(e)d" word, there is no intrinsic quality to indicate that it is a participle either. It needs to be hitched up with another word to take on that function.>

So we cannot also say that "bathed" is the past simple form of the verb, right?