Apologies for the small novel.....I just need a bit of advice

I have a little red micra that I bought nearly 2 years ago as my first car (which made a few question if id lost my mind) When I bought it it had 68,000 miles on the clock and is a cat C. It is now just fresh into 91,000 miles and it has never let me down for long. My family members call it Christine, if you know you know.

In the past half-year the repairs and services have been really what anybody would expect with an old car due to wear and tear - a new battery, new brake pads/discs&caliper, 4 new tyres, all fluids replaced (including transmission fluid - it's a cvt), new track rod ends, some jubilee clips to stop an annoying heat shield rattle, new air filter, ac resistor and cabin air filter. In total I've not spent anywhere near over it's original buying price on repairs, so I'd say it's almost paid for itself in a way.

It has showed it's s*** side a couple times whilst I've had it though; it broke down slap bang in the middle of the road from the old battery going bad, it also cut out being put from park to drive on a dual carriageway (pulling off from a layby) however sprang right back to life when i restarted it, still unexplained. Only once has it ever flashed its engine light at me and that was when I had kickdown engaged for a bit too long going uphill with extra load, it went into limp mode, I fiddled about with the battery and again she sprung back to life with no further complaints and this was about a month ago.

I have noticed that its becoming a bit sluggish lately. I did change the air filter quite recently which gave it it's signature kick back, but I can't help but feel like something is amiss. I have an OBD reader and it isn't throwing up any codes, and idle speed is 800-840 everytime I check it.

I've read up and I've seen a number of people mention that the throttle bodies on micras commonly go bad or play up because of grease and dirt. In the same sense, I also noticed that in the cold weather it feels super heavy even when fully warm - around 30 mins of pure driving (We've had snow and only -1c to -3c temps) which is leading me to believe it could benefit from new spark plugs too.

At low speeds I can really feel the gear changes but only when it's changing gear from 20mph and under. This frankly terrifies me because I've heard baaaad things about CVT gearboxes but then I've heard that a lot of people tend to not think to change the fluid, making them go bad prematurely.

A mechanic also told me that my 'timing belt' was perishing (micras have chains) to which I found that he meant my water pump drive belt, it isn't slack it just seems very slightly frayed on the top layer.

I know most people would just tell me to get a new car, but I'm not in the position for that yet so I'm trying to prolong the life of what I've got.

So, in the new year, what would you recommend I get looked at? All of it? None of it? What would you put higher on the importance scale? Bear in mind that if the CVT gearbox goes, it's a deal breaker and it's gonna be turned into a metal cube because fk that :P