yeah -all that is valid. i also think that it is not "evil" but very much in pain from watching the animal get the love you should have gotten. natural that that would cme back in the ways it is. i also went through that with my own pets - very painful and traumatizing cuz i was a kid at the time and making my pet need and fear me and felt i was also evil and a monster.
all processing the horrors of daily life. good that you are noticing it and CHOOSING not to act on the killing - like it was said, because i too believe that is your core part. Hard to deal with all that.
much support to you mouse!