Like Roger said, a lot of that is probably unknown until the SLI is done, but a fair amount of what you were wondering is covered in ALPA merger policy and in the TPA.
First, the TPA is pretty clear that any aircraft on property, firmly ordered, or held by option, belongs to the Company who had it on their books at the time of the merger. So that's 290(ish) 737s to Alaska, and 16 717s, 18, 321s, 24 330-200s, 10 330-300s, and 12(+8 options) 787s to Hawaiian. If they have been delivered or not plays no bearing in the math of total aircraft.
When I mention not straight DOH, I don't mean fences. Remember that there are 3 legs to the ISL stool... Seniority, Longevity, and Career Expectations. And in pretty much every merger since ALPA policy has been applied, Career Expectations is all about widebody flying. I think both properties are pretty similar on Seniority and Longevity, so that just means the Career Expectations comes into play. Who knows how that will get negotiated or arbitrated, but I doubt the list will go together based solely on date of hire. It is likely (unless they just toss a fence on the book widebodies until the most junior pilot at Hawaiian on December 3rd 2023 has the ability to upgrade... which is very unlikely) that there will be some rearranging of DOH via stovepiping or something similar.
I'm not sure how active your Merger Committee is in answering DARTS, but ours has been really good about questions like this, so that might be a good place for you to go to get some feedback on your thoughts.