So in my dialect of English at least there's a subtle difference between "we have confidence in you" and "we trust you". Even though in many cases the two can be used synonymously, "trust" can have the added connotation of confidence in someone's integrity specifically rather than just their ability. Is there a way to cash this out in Irish as well?
There are only two spoken exercises with asaibh, and as they're both spoken by the same person, dialect differences don't apply. The /asəvˠ/ pronunciation is basically correct for all dialects, whereas the /asəi/ pronunciation heard in Tá siad bródúil asaibh appears to be a mistake.
"iolra" is the Irish for "plural", and "iolra" doesn't occur in "tá muinín againn asaibh"
"tá muinín againn asat" means "we trust you", when you are addressing a single person, and "tá muinín againn asaibh" means "we trust you" when you are talking to multiple people. The "you" is plural, but the plural is implicit, not explicit, and is never spelled out.