Would say Syria reclaiming a large part of the Golan is possible, but don't think it would match the exact borders as fighting tends never be that clear cut think Syria can come ahead this round.
By that the Golan besides it's great defensive terrain used to be of Syria's richest provinces, rebuilding it will be a long and costly process, specially given the value of water I think Syria would need to fight hard to keep. Not saying it's pointless but think a victory where say Syria struggles and is willing to re-examine what went wrong and were they need to improve is just as vital to keeping it as say funding from other states to help rebuild it afterword's.
Would the arabs take back the Golan heights? Any of Palestine? With the PLO ruling Jordan, does this mean that they never go to lebanon and there's no Lebanese civil war?
The PLO was a big tent party of....a wide variety groups? It's difficult to explain but the PLO in Lebanon was already well established long before many groups were expelled from Jordan and while the PLO definitely helped start the Lebanese civil war it had decades of build up. Many of the PLO groups were controlled by Syria would go harass and launch raids into Israel who in turn would bomb the general population hoping to turn them against them.
With a Jordan ruled by a PLO that's very allied to Syria, hoping to keep their gains from 1973 you might see a cautious détente in Lebanon as in Syria order's its Palestinian controlled factions to stop in hopes of proving themselves a rational actor to Israel to get a treaty and Lebanese hoping the the refuge camps will come down. Note this will be a slow process, Jordan was in general for a long time before the Israeli invasion of Lebanon as more risky. The PLO taking over Jordan I think would have Palestinians in Lebanon be both a bit elated but also very worried about a potential Israeli invasion and not be willing to cross the border just yet afraid of being expelled once more.
That said, think a lot of Palestinians would be willing to move out of Lebanon sooner or later given the discrimination but think Lebanon might be soon having a crises soon between the many tensions in the nation boiling over, a Syria that's regained the Golan might be satisfied for now but think they would making sure the PLO in Jordan don't have full control over the camps might help contribute.
Overall would say the scenario is better than 1973 for the various Arab nations and people overall but they must do their best to maintain it and Lebanon is still quite fragile.