1. What purpose does the numbers on the action tiles serve, is it just an indicator of the relative value of the action compared to the other actions?
These indicate the player order for the next round, but are not used in Standard Steam since you bid for order (and actions) at the beginning of every turn.
2. What (and when) do you use the pass option on the Urbanization and Production tiles for? The rules state that when picking thes two tiles, you have to take the action. But why would you choose those actions and not upgrade a town/place new goods in a city? Also, if you wanted to 'pass' - i.e. do nothing specific - in your turn, a lot of the other tiles would serve that purpose.
In Standard Steam you may pick these actions and then decide during your turn in the building phase to not perform the action (if f.e some one else build a link you needed). In Basic Steam you must decide whether you will perform the action or not at the moment you pick the action. I've not yet seen anybody not perform the action, but maybe it's a good move to block some one else from taking it and delivering goods over his 6-link.