You won't lose anything simply by leaving the cloth room. The simulation remains in memory until you deliberately clear it, calculate another simulation, or delete the sim altogether.

Yes, you can export the .obj file for later import into ProPack. I usually export from the pose room, but I suppose that function works from the cloth room, also.

Alternatively, you can spawn a morph target for that prop, then save the prop directly to ProPack's runtime library. Cloth sims may not work in ProPack, but morphs spawned from a cloth sim will.