Welp, I had written a huge post but it got eaten up by the idiotic connection in this cafe
Anyway, here's the main lines of what I written :
Build naval buildings level 4 (or 5 and 6 if you can) in a few provinces for maximum ships production
Build naval building level 1 (docks) in all your colonies with tariff for a 25% boost to production.
Build production building level 3 in all your colonies for another 25% boost to production.
Use all remaining money not spent on magistrates at the end of a year to build light ships (do not build galleys or transports as they do not count toward sea lane protection).
Try to bring your inflation down by -0.10 a year if you can afford to (national bank + a Master of Mint should enable you to do so without losing too much income to do the rest of this list).
I would suggest making a new save file just to examine the difference. Thus take note of your investment total in your finance screen and compare 10 years down the line by doing this. I think having caught up in tech and being host to a powerful economy would be a decent end goal for the game. I'd love if you could PM me the results of this, as I'm no expert in Eu3 and would love to know if what I said is worthwhile
It seems to make sense in any case! Having gotten myself out of an ugly economic pit in this game, by expanding too fast and forgetting to consolidate my economy, I absolutely believe that you can save this game with the time you have left.
/edit/
Oh, another thing that I forgot to mention : if you do not mind not having a particular edge in any given tech field, since you should be able to field pretty strong armies in any case, you should be able to put all sliders in the tech investment window at equal value.