They were mainly experimenting with super soldiers just before WW2, so if he was around during that time he'd be approaching 100 years old, give or take how old he would have been when placed into the experiments. It's possible they used children at some point, although given that they wanted super soldiers right that minute it would be unlikely that children had been the focus, even if we wouldn't put it past the Nazis to do so. The "super soldier era" was sort lived after their failure to make much progress, but I suppose it's not 100% impossible to claim that he could have survived that long as a result of the experiments (that being a super rare case), or that there were still some attempts made afterwards using what they had learned during that time, which was mostly what not to do. If he was in one such experiment that was more beneficial, it was already too late to be put into use during WW2, or perhaps on small scale and covered up after the war was over. Him being a success wouldn't have made much of a difference in the grand scheme of things. While they might not mind sacrificing hundreds of test subjects for the success of one super soldier, the Nazis fell apart at the end of the war and Himmelreich went into hiding, halting a lot of the progress. The most likely people to get their hands on it after that point is the Russians or maybe France after occupying Germany after the war ended. If the research fell into French hand then that would help explain why they have gotten so influential lately. 

The men and their testosterone levels/decreased masculinity vary. In your guy's case he might be suffering worse then others. You are not going to get through one of the Nazi experiments unharmed, after all. It wouldn't surprise me that he'd have to take a boatload of pills every day.

EDIT: The characters are accepted.