Is it OK to change mistakes/typos when you are in the minor revision stage of publication? What I mean is to change mistakes/typos other than the proposed changes your reviewers pointed out to you.

As this article is based on a previous thesis (which had a very similar focus, only it was oriented towards a different cultural context) I've noticed a few paragraphs that could use a clean up (for example it would help to clarify that I use a certain term because it is related to the administrative divisions in my country,etc.).

I also noticed a typo on one of the results on the table that got carried over to the abstract. It doesn't change the results or findings or anything, basically it's just a decimal that should be lower.

My question is, would it be OK to change them now? And in case it was should I let the reviewers know I cleaned it up or go through each change, besides the ones they asked me to do, obviously.
Yes, this is completely OK. You are not bound to perpetuate typos from earlier versions just because reviewers did not find them.

It's always good to indicate that typos were cleaned up and similar, though you shouldn't note every single typo. I'd write something like "we corrected typos, especially in section X, and tightened up the prose in paragraph Y" in the answer letter - just to make sure that nobody thinks you are trying to smuggle in larger changes.

Of course, there is a bit of a gray area between small and not-so-small changes. If you want to change something that goes beyond simple spelling errors or awkward prose and starts to change your argument, you should draw the editor's and reviewers' attention to this more explicitly, since they should really sign off on any not completely minor changes at this stage.