Skill Discussions

I would say you are more of a Minmatar pilot than a subcap pilot. To me the term "subcap pilot" implies all races. But congrats on having the discipline to stay so focused.

Shield Management kinda stands out as needing to be at V. Maybe missile skills after that? Armor compensation skills to V is also a good idea. Also everyone can use a few levels in accounting and broker relations since everyone sells things from time to time. Maybe train up some ewar skills? Several Minmatar hulls get a bonus to target painters and TD's are great even without a hull bonus. Perhaps armor layering?

Did you look at the character sheet?

Unless our browsers are showing it vastly differently... everything already is at V

Well, your missile skills would supplement the minmatar setup.
Not a very large SP to usefulness ratio, BUT if you opt to go for a tengu for the versatility you should get a lot out of it.
Focus on target navigation prediction, guided missile precision, heavy assault launchers, light missiles.
You get the best out of caldari ships through that route, HAC's cruisers, Tengu SC.
Your entire E-war section could use expansion, target painting for missiles and the rest for the spare high/disruption setups.

are you joking? or...
...
are you serious?

What goals you seek to achieve? You got any goals?
Is your goal to train a character for the character bazaar?

After looking at your character sheet, I got the impression that this character has obviously hardly ever undocked from station.
Usually I look at character sheets and immediately see in what they "specialize" in. Your character rather follows bluntly "level-5-ing" with a lot of wasted skill points for a 70M character, while other crucial skills are entirely lacking.

However, in order to plainly answer your question, "which skills to improve to make me a better subCAP pilot?"
Train all skills that do not have higher or exact training multiplier than x12 and do not have the word "capital" in their skill name. I mean, what else one could suggest with such a character sheet?

What do you like to do in EVE? First figure out what your interests are, and then train skills in order to maximize your performance in that area, and only focus on the those selected roles...
If you rather enjoy training and not so much the playing, then just train, train, train...
You have still around 12 years ahead of you to max. out your character...there is still so much to train for, no reason to get that much specific and detailed about the skill training order...in your case...

And about your question concerning the nanites:
Do you even overheat? Nanite paste hardly takes any cargospace...
Nanite Operation level 3 would even be fine for almost everybody...
It is Nanite Interfacing that would be worth training to level 5 at most.
Players could and might have 200M skillpoints and still have Nanite Interfacing and Operation both on level 4...

Very strange character...

Yeah, the masteries will be a fun new goal to aim for.