There is no way Disney would ever be allowed to buy all of Sony. I don't understand how they were allowed to buy Fox but the Government gave them the ultimate benefit of doubt and let them gain over 40% control of the domestic box office. The government can't stop them from getting Spiderman and family back to Marvel but that is it. Anything more and they would own over 50% of the domestic box office in a bad year and 2/3 in a good year. That is unacceptable to anyone who cares about competition and the free enterprise system.
So far this year, according to box office mojo, there have been 638 movies released. Disney and Fox have combined for 19 of those movies. That is 2% of the total and hardly market dominance. The fact to which people go to watch the 19 movies vs the other 619 has to do with the content and movie experience. Disney isn't doing anything to make these other movies less desirable, or mediocre from a box office perspective. Anti-trust law is about access, and opportunity and predatory behavior. The Anti-trust division of the Justice Department made their decision based on movie count and market access.
Getting Spiderman "back" means getting the remaining "rights" Marvel had licensed to Sony back. Spiderman is an asset on Disney's books. The exclusive rights are the asset on Spiderman's books. There isn't any real Anti-Trust issues with re-acquiring these exclusive rights for an asset which you already own.
The economic model Disney uses to value these "exclusive rights" in an acquisition, is the same Disney used in acquiring Lucas, Marvel and Pixar... The Discounted Cash Flow model is the same, but the resulting value is going to be much lower, because Disney has successfully re-established its rights for a great deal of the Spiderverse, including Product Licensing, Broadway Productions, Short Duration Annimation, etc. Unlike prior acquistions, the movies are the only part of the acquistion which would produce incremental cash flow.
One part of the acquisition model takes a look at what the value of the Spiderverse would be vs other existing "similar" assets. Disney has so many un-used Marvel Assets, which it could leverage the same way. The 4-5 billion dollar price tag would be a huge over-payment.
I think an objective look at the value of the Spiderverse over the next 10 years, also has to assume participation with the MCU and the value this linkage has in the current valuation of the Spiderman character. Venom did well, and may replicate its performance in Venom 2, but if linked to the MCU it is arguable Venom 2 would be a multiplier higher in revenue because of the relationship to the other known characters. Sony knows this and its why they are pushing the Spiderman cameo.
As for purchasing the Vue Streaming subscribers, the cost of integration, and the resulting lower price point Hulu would recieve (there is likely no difference in price they could charge) for those subscribers makes such an acquisition a non-starter. Heck there may be an overlap between the Sony and Hulu subscribers. Disney could put the same revenue into advertising and pushing the Hulu product and get the same subscriber volume and probably a whole lot more. I just don't see an economic rational.
Lastly, if Disney is patient, the rights to the Spiderverse will revert back. Sony will have to make an acquisition or get out of this business to keep it profitable, either one of which could result in a change in control of the exclusive rights. Sony appears to be cash starved and struggling on so many fronts, as the Streaming Wars advance, it will be harder to stay in the race.