...If he resigns, it will be after the election. He's skimming off of the campaign funds and using the office for his personal gain (not to mention he gets free body guards afterwards...its well reported he eats fast food because of the difficulty in poisoning it...and if he's that scared already, then he's got some serious problems).
Once he loses, then he'll get what he can and resign. And Pence, whose political career is now over since he chained himself to a dead prostitute, will pardon him. From pressure of other rank and file GOP. Investigations can be drawn out for years and hurt the party for years. A quick and fast pardon essentially ends all of that.
Sure there are state investigations, but a Federal pardon will complicate things. Particularly if the crime is not just a state issue but Federal. And if they find a crime with a good separate boundary, it will be tied up for years in appeals and states don't have the resources like the Federal government has. So they'll probably abandon the issue and move on to something that is more of a slam dunk.
Trump and family is going to walk. But they have another problem. The name will be toxic in the business world. Once Trump keels over, it won't surprise me the family becomes adversarial to each other, take their portion.....and sell it off. They will reinvest quietly without the Trump name, become silent partners, etc. Won't surprise me either if one of them loses everything in the end.
Trump built up his brand....and in the end, destroyed it. He has no legacy after this.