Concerning trade (apart from the trade company merchants, which Laurent already answered, and the general collection set-up, which you're going to look into): the Trade idea group grants 3 additional merchants by itself, plus trade power, efficiency, steering and so forth. Plus some great policies for that trade money influx: 20% trade efficiency with admin or quality, 20% goods produced with quantity, all of which you have.
Unless you're still colonising, and you have serious problems with your economy, consider dropping Exploration ideas and grab Economic for additional cash, and cheaper buildings (plus the +5% discipline policy with quality, which might help with that war with Russia). The cheaper buildings might also help you finance state houses and town halls to deal with your governing capacity.
On that note: what are your current sources of governing capacity? Specifically: have you granted your estates the privileges, and have you taken the government reforms granting additional capacity? Those would be easy short-term sources. If you're already done with all the government reforms you want, dump all your current and future reform progress in additional governing capacity.
Additionally:
- What advisor(s) are you missing? At your current size, I suppose lvl1 +10% tax/production efficiency, +10% trade efficiency or -10% army maintenance would all be a net profit for your finances.
- Do you need that 60k merc army? You look like you have enough manpower to disband them and hire cheaper regulars.
- For a short term economic boost, mothball your forts that are not under threat from those soon-to-spawn rebels and reduce your army maintenance once the rebel threat is over. Or even just delete some forts in place that will never be sieged anyway. You can use the money you save using that to pay off some loans or build economic buildings to boost your income.
Since you mention it: what is the source of your corruption? Boosting your economy allows you to spend more on combating it, but taking care of the source should at least stop it from growing further. You get a natural decrease in yearly corruption from stability and being ahead of time in (admin/diplo) technology.