You can get one FP. Then a second when the return window on the first opens or two hours after getting the first, which ever is sooner. You can use your FP anytime after the window opens, as long as you use them the same day. Thus get 6 during the day but not using any of them until 9pm.
Roger Rabbit is not connected to the system, so the above rule about the opening window or two hours later doesn't apply. You can get a RR FP a second after a SM FP, if you can run fast enough.
DCA is not conneced to DL so what you get in one park won't restrict when you get another one in the other park.
Also WoC used FP machines to distribute tickets, but they aren't part of the FP system and don't affect FP collection at all, so I try to refer to them as WoC Show Passes instead of FPs to differentiate them because they technically aren't the same thing.
Another thing to keep in mind is to use a ticket to get a FP, you have to enter a park with that ticket(making it active for the day). So once a ticket is used to enter either park, it can be brought to and FP machine in either park and used to get FPs. Hence the group can enter DL together and a runner can be used, with the runner taking all the ticket to DCA or any other FP attraction, without the whole group not needing to go with.