My issue is that the Legendarium, as a mainly phylosophical work by nature, has a lot of stuff that's subjective and open for interpretation.
For instance, "being a weapon against Ulmo" might not necessarily mean Ossë could actually hurt or fight him in an actually meaningful way, but rather his demeanor could be a threat to Ulmo's domain, to his creations and the likes. Mostly every corrupted Maia who fell to Morgoth's side could easily be considered as a "weapon" against the Valar in that context.
On a similar note, Morgoth fearing someone should not to be immediately considered as a show of that someone's might. He was shown to be quite cowardly at times, fearing his confrontation with Fingolfin even though he clearly had the upper hand during the fight, and killed the elf lord. He was also explicitly said to fear the elves of Gondolin and the races of Men, and they certainly are no match to the Valar and wouldn't be anywhere near Universe level.
Besides, the Dark Lord fearing Arien, who albeit a Maia, was the Guardian of the Sun, is not exactly unprecedented. He fears the light and the warmth she brings, and then "with shadows he hid himself and his servants from Arien, the glance of whose eyes they could not long endure". Which makes sense, for Arien's eyes were said to be too bright for even the Eldar to look upon.
Essentially what I'm saying is that maybe these statements don't actually translate to raw AP/tier scalling, and rather have a more thematic/subjective meaning behind them.