Just try to create good content by yourself and do not stop to update your website. I've also got small money from adsense
Happens a lot lately. Google is keeping more money now. One of my sites (loans niche) used to pay $1 per click, now i get $0.01 all the time, the best ones go to $0.20 max.
I don't think this is a case of Google keeping more. Since your "niche" is a common MFA one, I bet a bunch of those type of sites have ads squatting on your page rather than legitimate ones.