"d) Is there any downside to putting everything through static port?"
Yeah.. You have multiple devices behind pfsense do you not.. So client 1 goes to pfsense.org:80 from his random source port of say 42103… So say 192.168.1.100:42103
pfsense using napt creates the connection from publicIP:port to pfsense.org:80
So if always used static and pfsense used same source port as your client so you had publicIP:42103, what if client 2 or 3 or 14 wants to talk to say facebook.com:80 and it just happens to use that same source port 42103 -- how does pfsense maintain both connections? 192.168.1.122:42103 It can't!!!
Now if you had only 1 client behind your nat wouldn't be an issue because well clients not going to use the same source port to connect to different places. But the more clients you have behind pfsense the more likely it is that would run into issues with clients using the same source port in a conversation to the public.. So your going to break shit if you try and force all ports to static.
And since machines to when started start at the beginning of the range and not some random part of their Ephemeral port range - while different versions of OS have altered what range they use, etc.. if you had a bunch of window 7 machines that all use the same range and you rebooted them say in the morning everyone turned on their machines - you would have a shit storm of why does internet work and then not work and then work why is it SLOW, etc. etc. etc.. And connections were attempted with the same ports and pfsense set to use static couldn't make those connections.