The value of a trade is that it gives you an alternative if sitting at a cubicle for 2000+ hours a year drives you crazy. Plus, it's always good to be helpful. You may want to look into becoming decent at auto repair or carpentry. Those are things that typically have a much higher barrier of entry, and a lower salary than HVAC, but they're both always a helpful skill.

The value of a second language is it opens up travel opportunities, and if you choose an economically important language (Chinese, German, British "English" [I have no idea what they're saying...]) or a politically important languge (Middle Eastern languages), the pay can be quite high for translation.

Many here might think HVAC is a terrible idea, and they may be right, but I'd still recommend finding a trade and making it a hobby, like I mentioned with auto repair or carpentry. Learning a musical instrument is also a great way to improve your life in general. But for the most part, sounds like you have a good head on your shoulders, and you'll do well at whatever you choose, so long as you stick to it.