sorry I dont really have time to answer this question properly/fully , but given no one else has jumped in...
ive not looked at the patch in depth but it uses tables record/play
so the answer to your questions really all revolve around that startpos is a float 0.0...64.00, and has 28 decimal places.
the best way to think of this is a %, where 64 = 100%
as such the play has no concept of playing a part/loop it carries on playing till stopped
so the patch is basically just restarting it, at an appropriate time.
again this is is all floats, so you should be able to go quite small.
what I would do, though not the easiest way...
is actually write a new patch, using record/play, and build it up, you can then look to this patch for inspiration.
the advantage is, you will have a clear idea what its trying to do, and the states its getting into.
in some way its harder adapting others patch (unless they are documented well... = never ) than writing you own
Im a bit surprised if there are not loop/slice objects in the community library, Im pretty sure a few people have been doing this.... its not super hard, but does have quite a few 'edge cases'
sorry cant be more help at the moment,.