It's normal to see fluctuation in subs count as YT performs regular checks and removes the spam account from your subscriber count. More info here: https://goo.gl/vaHoKS . Hope this helps clarify.
Hmm, please send a feedback report directly from YouTube with these steps: https://goo.gl/WdI0BK . While every individual report may not get a direct response, we do review everything and use the details to investigate and fix issues. Thanks.