Snejdarek, I can help you out here
The Cops are right two times and wrong to times:
Knives of any kind are legal to own and to carry how and wherever you wish. If you want, you can carry a Katana around. Any kind of "rambo knife" is also legal.
The only exceptions are "hidden" blades (looking like another object) such as sword-canes which are forbidden, and you also can not carry during a political demonstration etc.
A "Totschläger" is a baton/stick(?) with an extra weight on the "hitting end" like the one you posted. As long as a collapsible baton does not have that weight, it is considered a "Schlagstock" and therefore legal.
Dashcams are forbidden by strict interpretation of the law (you may not "systematically tape" in public), but there is no fine the police can give you on scence, they very very rarely forward it to the courts and anything you tape on your dashcam can be used in court if necessary. So all in all the typical silly solution.
As for the Vignette - you are right, you should have bought it at the last gas station in Czech Republic (I belive, there are supposed to be signs on the highways reminding you), however it is idiotic of the Police to fine you right after the border for that. Our police sadly is notorious for things like that, they really like to cash out tourists especially from Germany and the Netherlands (as there are so many of them passing through on their way to Italy) with that tactic.