I didn't see a "Finch Counseling Couch" section, so I hope this is okay for the general questions area.

I have a male Zebra finch named Jackson.
He's 7 years old and his mate Maggie just died about 2 weeks ago. They had been together for about 6.5 years.
Jackson lives with 2 other zebra couples.
One of the other couples has a 9-10 day old chick. (This is actually Jackson's biological chick; but the other couple started sitting on the eggs once Maggie died -- they basically comandeered her nest.)
So, lots of upheaval in my flock lately.
Jackson is NOT taking it well and I don't know what to do.
He used to enjoy being handled. I'd put my hand in the cage next to the perch and he'd "step up" onto my finger and I'd take him out for petting.
Now, he wants no part of it. He'll either fly away or nip me -- a very clear "back off."
The most disturbing part is his OCD-ish behavior.
For the past several days, he's been on an OCD tear. He's flying back and forth between his favorite perch and the corner of the cage incessantly.
Back and forth.
Back and forth.
Back and forth.
(And it's a very quick back and forth; he barely touches the side of the cage before changing direction and returning to the perch. It's about a 2 second round trip.)
It's dizzying to watch.
He literally does this for hours on end.
It seems he only stops to eat or sleep.
I feel awful for the little guy. I'm assuming it's behavioral as the flock dynamics have changed a lot in the last couple weeks, with his mate Maggie's death and now, the new chick.
He doesn't seem sick in any way.
Is he upset by the baby?
Or is Maggie's death upsetting him?
Normally, when one dies, I get a new bird within a day or two. (And to be honest, the mate of the deceased has never seemed all that bothered.)
I haven't gotten a new finch yet due to the chick. The pair that's caring for him is a bit snippity with the others when they come near the nest and I thought adding a newcomer would be a recipe for a pecking war.
Plus, I know that stressors can cause them to stop caring for the baby properly.
Any ideas on why he's acting like this?
And more importantly, any idea of how to help him?
I hate to see the little guy acting to nutty.