He had enough charges lined up (up to 5 years for every count, IIRC) that he would likely be imprisoned for life. Goes without saying but he was also an incredibly paranoid person.
That said, he was 75, so I guess even a few years could potentially be a life sentence.
Usually, without aggravating circumstances, federal sentences would run concurrently, though thr multiplicity might push them up within the range permitted. So, lots of nonviolent up to 5 years per count crimes with no particular extreme factors likely adds up to...about 5 years.
Which at his age might still be a sizable fraction of his life, and he wouldn't be the first person to act based on an unrealistic estimate based on what is theoretically possible rather than likely.