Hello Schreib,
I've watched the demos, with the suspicious times, and to be honest i'd say that for most of the time, you are doing way to much sound for him, if he is using sound which is probably the case, he can hear you easily because you are not sneaking , but jumping and doing known speedjump which he is looking/linning at and expecting you guys to come from. You are complaining alot for nothing but a good play in the demo, that's sad. You should focus way more on ur gameplay instead of others, and understand how he did that. Thats my thoughts. But i understand that sometimes, you can be suspicious at someone and expect him to cheat, especialy on DP, but for this one, i doubt that he was using one.