It's likely not just a +20 to your monthly income, because if it is, it's not working. So, how does it work?
reign in italy and then keep the peace in the empire (spam enforce peace and return land demands). Then expand into the remains of venice and bosnia/serbia, and reduce as many princes as possible into OPMsHow were you able to enact 4 reforms that early, without expanding much for as far as I can see?