You've never heard of this because it's not true. A note wants to resolve up or down based on it's relative distance from tonic. This had nothing to do with what it's named, the most important part of naming notes is not repeating letters in an 8-note scale.
> taking one example, F# "wants" to step up to G, whereas Gb "wants" to step down to F.
Uhhh....no? A flat or sharp can be the tonic, which does not lead to any other note. A note is named flat or sharp to maintain proper interval distance without repeating letters within the scale. A flat is typically not a leading tone because of interval distance, but can still want to resolve up or down. Any note can be consonant or dissonant, leading or resolved depending on the context.
Music theory is really a domain specific language. Like all languages (not programming), the only way to really learn is to converse with others. I don't think you can learn theory alone, it only makes sense when you talk about music using music theory with other musicians.
1) Talk to a lawyer. Details are going to vary wide depending on where you are and the documentation that exists.
2) Your work has value, quite possibly more value than the capital put in by Jim.
3) If you own 40%, Jim has to buy your 40%. You position as a shareholder is not related to your position as an employee. Ownership doesn't disappear. I don't quite understand how/why you would reduce to 5% from 40% (without dilution events).
4) Don't sign anything until you talk to a lawyer.