As for point 1, I believe Solasta Crown of the Magister has a small bar of numerals come up when you click on a spell, which allows you to just click which level you want to cast it at.
In fact, it would be much easier if spells weren't on the hotbar at all. I think it makes sense to have a section of the UI dedicated to holding all of your prepared spells, with a tab for each level (Cantrips, 1st level, 2nd level etc...). That way you could very quickly and easily navigate to any spell you want to cast without having fill pages and pages of hotbars with spell icons (especially when they're already cluttered with potions, items etc...).
With point 4, I agree that trying to cast Charm Person in front of other people would cause suspicion/conflict (like it does in D&D since it has verbal and somatic components), but if you're only talking to one person then it's usual risk-reward - will they make the Wisdom save and know you tried to manipulate them, or will it work and give you advantage for the conversation? Much more interesting decision than just "click persuasion check dialogue option and hope for the best".
