You know what... this is a theory of a couple things. Not everything. And you should number your questions, it'll be it easier to respond.
1. Q:
What mechanism is it that results in "light isotopes being issued forth from the white hole horizon"?
A: White hole baryogenesis. Described previously in this
post.
2(1). Q:
What are these "light isotopes"?
A: Hydrogen, helium and lithium.
2(2). Q:
What is their relative abundance?
3. Q:
What is the distribution of velocities at which "the light isotopes" are "issued forth from the white hole horizon"?
A: Good question, no answer. Asking about processes that occur behind the event horizon are damn near impossible to say anything about.
4. Q:
How is this distribution derived?
A: See above.
5. Q:
What is the mechanism responsible for the "eventual smoothing of angular momentum"?
A: The changing G and c.
6. Q:
What is the evidence that "spiral formations [...] dominate the universe around us"?
A: Spiral galaxies dominate the local area and it appears to be an
evolutionary trend.
7. Q:
Where, in the evolutionary sequence, do irregular galaxies come?
A: Gravitational interactions.
8. Q:
In this ATM idea, do all elliptical galaxies contain an AGN?
A: Originally, they can eventually be exhausted.
9. Q:
If not, how do the ones without an AGN form?
A: See above two responses.
10. Q:
OK ... but I presume you are prepared to answer questions on the observed distribution of angular momentum in ellipticals, and similar questions, without referring to CDM; is that so?
A: Not really, no.
11(1). Q:
Finally, how does this ATM idea account for the observational fact that the proportion of late-type vs early-type galaxies changes, as a function of z (the redshift)?
A: The universe is expanding? This isn't being debated. That's still in Shu's paper, he just assumes contraction as well. It's all relative though.
11(2). Q:
What is the role of galaxy collisions/mergers, in this ATM idea?
A: And collisions/mergers just happen.
I also expect that white holes can 'calve' and divide their event horizon as the masses of the gravitionally interacting light isotopes exert an outward and uneven pressure on the event horizon.