Adjustment of the Lachmiller/RCBS tool for decapping is quite finicky. I'm sure there's a better explanation on line than I can give, but start with the decapping pin too deep in the tool to successfully hook out a primer. Hold the case in a seating die, not the case holder they supply. Use the allen screw to advance the decapping pin gradually, until primers come out. You will not get 100% of them. I break a de-capping pin every several hundred cases, but you can resharpen.
The early Nazi-era cases I have used do not have a primer crimp or sealant. Some makers crimp and seal their Berdan primers such that you will not get a significant fraction out.
Hydraulic removal works. There are a number of ways to do it. One is with a hand-held ram, but it has to fit the neck tightly. You can probably get away with putting the fired case in a ordinary case holder. I have had machinist friends make a number of rams for me. Another hydraulic method is to remove the recap pin from a full length size die, size the case neck only, fill the case with water, insert it in the press ram's shell holder, raise the case until the neck expander starts to enter the case mouth, then move the ram up smartly. Much the same can be done with an appropriate sized "M" die. There are also specialized hydraulic tools such as my friend Shlomo made several of for me, God rest his soul. All of these are best done outside in warmer weather.