I wouldn't worry about getting a Tetanus shot anymore often than every 5 years, but I remember hearing about a study where they found it very rare that anyone got tetanus after having been immunized at any point in their life. I need to google that.
The crappie from deep water thing is interesting. They can get back down when yanked from 25 foor down or so, but deeper than that and they are going to have issues. In Texas, they waive the 10 inch minimum on Lake Fork, Lake of the Pines, Toledo Bend and maybe Sam Rayburn. You MUST keep the first 25 crappie you catch. No C & R fishing.
I have put some smaller crappie in the livewell and they have recovered over the course of the day. If you put them back and they don't get back down pretty quickly, the gulls, loons, peilcans, or cormorants will eat them.
I'm sure you could "fizz" the crappie, but oddly enough I've never seen an article that stresses catch and release for crappie.