Regarding Frankfurt airport's strictness: It's Germany's biggest hub with the most international connections, some of them more "targeted" than others (say El-Al flights...).

Regarding ICE's: That's one of the trade-offs. Either guaranteed (cramped) seating after being "violated" or un-violated uncertainty.

Every time I use one mode of transportation, I'll damn myself and vow to always use the other mode from now on.