POD could be propably the israelien election in summer 1981, were Labour instead of the Likud win the election.
Today it looks like, that Israel drove Belzebub (PLO) out and he was replaced by Satan (Hamas). Without the Invasion, will the PLO prevent the rise of the Hamas? Will Iran-Contra be butterflied away? And propably even the Intifada?
I think you are confusing Hamas with Hezbollah.
Hezbollah didn't came into being as a response to invasion but the invasion did radicalize shi'ia community to a greater degree. You already had splinering there as a result of both LCW and iranian revolution.
What happens is that Iran continues to fund more radical elements but PLO keeps a tight lid in the south so shi'ias operate in more restrictive environment.
Amal may become a player but nowhere near the size of Hezbollah. hezbollah gained street cred by spectacular attacks agaisnt foreigners. Without foreigners they lack targets of sufficient value and attacking fellow Lebanese insuch way might be counter productive,specially if directed againt other muslims.
As for Hamas,they will likely rise as they had little to do with Lebanon. Israel would still try divide-and-rule approach and Hamas was the best option. What might happen is less prevalence of suicide bombings, since prior to mid-1990s they were shi'ia, not sunni thing.