You may want to double check that they issue the A&E FP/Return Ticket during EMH. Olaf uses a similar FP/Return Ticket system to A&E and like A&E, he is "disconnected" from the rest of the DCA FP system. So you can get an Olaf FP/RT and then immediately go get a A&E FP/RT (or vice-a-versa). The Frozen Sing-Along uses the traditional FP system, which means it's connected to the rest of the DCA FP system. In other words, having an A&E FP/RT, an Olaf FP/RT, and/or a WoC FP does not impact your ability to get an attraction/sing along FP.
There is no limit on the number of FPs you can have at once per se. Once you get a FP, you have to wait until that FP's time window opens or two hours elapse, whichever comes first. So for example, if you grab an RSR FP at 9:00 am and the return time is 5:00 pm to 6:00 pm, you can get your next FP at 11:00 am (two hours after you go the FP). If the return time had been 10:00 am instead, you could get your next FP at 10:00 am (when the time window opens). So you can have multiple FPs at once, it all depends on the return times. The only caveat is that I've read you cannot have two FPs for the same attraction.
