Loans is just a number which will soon vanish if you get money from wars, as early loans are extremely small compared to midgame income of an agressive player. As small starts locked between majors, you have to play agressive and to grow thin early on. If you lose, restart, if you don't, you become a big player before 1600.
The main issue here is that because you let some early possibilities slip you have no money to fuel expansion into valuable trade nodes, so you have less money, so you don't have manufactories, so you have less money, so you debase, so you are behind in tech, so you can't expand, so you have less money and you end up with less than 100 ducats of income and less than 5 from trade in 1625. You need to fix that asap.
Can you somehow get into Venice for instance? I bet they're allied with France or something like that but maybe you can use Austria. You need the income and getting Venice and Ferrara would almost double it instantly. Getting Astrakhan from Crimea would help, but I bet they're allied with the Ottomans, right?
You've been playing for a lot of time, you surely have lots of trust with Russia I bet. Over 90 trust they'll never go hostile due to wanting your provinces, so you can take their permanent claims in the Steppes.
I'm still thinking of how you can pull that off, but who are Kurland and Riga allied with? The Baltic is an excellent tradenode as well and you can get almost 10 ducats per month if you simply take Riga and move tradeport there.
Bohemia wouldn't help your economy even if that's better than nothing, you need many wars to get to their goldmine and Krakow would be a hell to control, just like Kiev, unless you also make the Baltic Sea your homenode and can transfer instead of collecting (we come back to having a good endnode). The Nitran goldmine will be key, however.
There is still the possibility of a no CB vassalize into India, and growing from there, but that's late to get the full benefit of it.
I don't have any other idea to fix a run with that income and that corruption in the Age of Absolutism, even if that's not lost.
Edit: And oh, do you have merchants estates in Kiev? The TP of the tradenode seems low, even considering the penalty from collecting outside of your homenode.