Hm, interesting. YANA doesn't really move me all that much and I can't say I've really heard the 'trembling' voice in it. Also not sure about him being in a weak and vulnerable position in the song. Is he? Pretty much never listen to it but think I'm gonna give it another go, pause and reflect. Maybe I've forgotten the details, it is a really long time since I listened to it.
DWA, I adore. Just love it so much. Definitely can hear the trembling voice in this one and, yes, 'really sad confession' just about sums it up. So moving. Sometimes when Michael does an emotional song he gets it slightly wrong, imo. He'll go a bit too far with the 'trembling' voice thing. I'm thinking of 'She's out of my life' and 'You were there' (although with that one I think there were mitigating circumstances and, of course, it's not a 'heartbreak' song, as such). But DWA is perfectly judged. Just beautiful. Fabulous example of Michael making a song so much his own it's impossible to remember that someone else wrote it. He does that a lot. Some people complain about him recording songs written by other people. Always find that hard to understand.
Also yes to the 'despondency' in his vocals in DWA. Of course, there's resignation in the actual lyrics but also, as you say, in his voice as he sings. I think 'sad despondency' sums it up a bit better, maybe, than 'heartbreak'.