Please see https://forum.renoise.com/t/missed-notes-with-pdc-as-rewire-slave/24934 why Renoise might miss some notes as ReWire slave. The fact that Fruity does not publish loop information just makes this problem worse (makes it happen on every loop jump instead of just while starting to play).
Unfortunately Fruity loop is kind of useless as ReWire master for sequencer alike ReWire slaves as Renoise is. That you can’t control anything from Renoise with Fruity as master is a big limitation. I think they added ReWire mainly for the MIDI routing, so that you can play for example Reason synths in Fruity in its sequencer.