You may need to start building various types of equalisers to have a better understanding how they work. Nothing beats practice.
Equalisers are frequency driven. If you alter one frequency the frequencies surrounding the alterd frequency are going to react. That is how all equalisers respond whether it is a DSP, transistor or valve equaliser.
Your slope is too steep and is peaking.
The Q is not wide enough to control the frequencies lower than 10 Hz and they are reacting to the sine wave signal being fed from VST Analyser.
Since there is no way to turn off the signal and adjust the measurements in VST anaylser you are getting a bouncing signal. The rise is due the frequency below 10 cycles returning back to 0 dB in which VST Analyser cannot display for it is limited to 5.3 cycles.
Slopes continue to decline per octave until it reaches DC or 0 cycles.
Peaks will not follow the slope method unless the Q is wide enough to cover various octaves, are set at a very low frequency and, offers enough dB loss to mimic the response of a slope.
MyCo offers an OSM with optimise filters which do not offer any artefacts in the link I offered.