Should, could, would

I've no idea how you overuse it but if it's a problem you could always stop using it and rephrase the sentence involved.

First, congrats on almost finishing a draft of your novel!

From all the unpublished work I've seen, I'd say most, if not all, writers have "tics": words, phrases, punctuation, etcetera that they like way too much. It seems they take care of them once they're made aware, though.

I don't think we are able to spot everything in our own writing though, and would never send anything out without putting it through several critiquers/or beta readers first. Although much of what is suggested probably won't work for you, I'm sure you'll also find more errors that you were unaware of.

Beyond that, it's hard to suggest alternatives for the specific thing you're talking about without actually seeing it. Good luck!

Overusing anything is a problem, but one that's almost always easy to correct. Such editing/rewriting is pretty simple, even if it can be time consuming.

Being aware of problems is the best way to fix it. Every time you use one of those words, rephrase the sentence accordingly. I had/have the same problem with "looked/gazed." Getting better though.

If you use an online grammar checker, that may tell you if you are using a word too often.

I use Pro Writing Aid and one of the reports they spit out is overused words.

You need a paid subscription for anything over 1000 words, but you can run a sample to see if it agrees with you.

We all have little writing tics, but use of words like should etc., can be an aspect of one's voice. It can also be a technique for attributing motives to a non pov character without breaking pov (it's a judgment word).

Beta readers can tell you if a word is overused or if it's used inappropriately. Programs can tell you numbers, but they don't do a good job of judging context or telling you whether a word use is irritating or distracting to readers,