Ok, from a singing perspective now, and purely that, it's clear he has vocal chord issues, either allergy or swelling or other reasons, because Jon is stuck largely in Chest Voice and it's why they are lowering the key. In singing, you need something called Chord Closure, its where your vocal folds close together to produce sound, and Jon is struggling with this, and leaking air so everything sounds breathy and shaky. To hit higher notes, you need a mixed voice, and this needs a lot of support and good chord closure, without it, the higher range is very hard.

I can sing Bon Jovi songs without issue normally, but this morning, I woke up with a slight sniffle, its not a cold, you wouldn't even know I have a cold, but that little sniffle has knocked my vocals out, so people shouldn't be so hard on a 60 year old guy who has been touring most of his life, things should come back.

I believe he suffers from Hay Fever, and checking the early shows, the Pollen count was high. Last night it was low to none, and I notice he had better chord closure last night, so I think this maybe related.

In terms of timings on some songs, this is where the inner ear pieces really knock your confidence. You know you sung the last verse bad, so you start over thinking, you effectively don't want to hear yourself, so you end up pausing before singing a verse hoping your not going to go to crap on it, and generally just over thinking singing.

Whilst it is horrible to watch a singer in this situation, I do feel for him, I think providing he can get his chords under control, he will return to a level of stability once again.