I don't think that the change of venue request was compelling. At the same time that they made the request the Trump team was bragging about how much NYC loved DJT -- a theme they kept hammering up to and after the verdict. The defendant doesn't get to forum shop. If you don't want to risk trial in Manhattan, don't commit the crime in Manhattan.
As for the timing of the various cases, it takes a lot of time to build a white collar case. And many of the delays in the various cases are delays orchestrated by the defense. Jack Smith has tried to get his cases moving much faster than they have moved, and the defense has delayed (with the great assistance of the judge in Florida). The Florida case was filed as late as it was because the government tried to work with Trump for over a year to get voluntary compliance. He got considerable time and deference that neither you nor I would have enjoyed if we had left government with those documents. We would have received a perp walk and jail clothing until trial.
I know the number of cases. And I know that NY courts have ruled that crimes committed under the laws of other jurisdictions can be crimes eligible for upgrade to a felony. Unless someone pays my hourly rate, I have zero interest in researching what number of those cases involved "expired" crimes (I assume you mean crimes for which the statute of limitations has run).
Prosecutors switch jobs. This isn't new thing. As for state and federal prosecutors talking, that happens in lots of cases. Unless and until we know what they were talking about there is no evidence of election interference. The NY attorneys may have been asking if the Feds had any interest in pursuing the federal campaign claims that Trump had his DOJ drop (clearly they either had no interests or believed the statute of limitations had run). They may have been asking for evidence collected by the DOJ regarding the campaign investigation. That would be a normal request without regard to the upcoming election. It is unlikely that the DOJ would have been so careless as to say "please prosecute Trump". It is more likely that the DOJ would have been afraid that the prosecution would faith and that in might may Trump seem more bullet proof to the juries in the federal trials. Prosecutors are very tribal that way.
If the GOP wants equal application of the law, why do so many of their arguments build on the fact that he is special because he is running for office (and/or a former president)?