So pretty much AuxPow is killing Doge faster than anticipated.
It is not killing it. On the contrary, it's bringing more security to its network. The fact that the mining profitability of Dogecoin alone is much lower compared to when Doge was not merged-mined is perfectly normal and expected, and causes no harm whatsoever.
Also, there was a big change of the PPS reward from 125 down to 115 why was that? What determines the reward percentage now?
As I've said before, the difficulty of the Dogecoin network is rapidly increasing, as expected.
[...] the PPS ratio will be adjusted to take into account the expected rewards coming from merged mining. [...] Of course, after merged mining starts the PPS ratio may need to be adjusted frequently based on factors such as the DOGE/LTC exchange price and the difficulty of the Dogecoin network, which is expected to increase rapidly.