is 2400 puzzle ratings good enough?

yeah

Hmm, I would probably say that chess.com puzzle ratings rarely reflect actual chess performance level, the most accurate way to see if you are grandmaster level is to get your rapid rating. 2500+ is grandmaster level on average I think.

Meaning 2500+ in rapid, many grandmasters are 3400+ in puzzles

If you desire the grandmaster title: 1. Get to 2500+ in rapid 2. Get lucky 3. Somehow manage to get three grandmaster norms, winning them is going to be tricky since many great players are going to be competing for them

I have heard there is kind of a rule of 17 in chess: that you should be at least 1700 ELO by age 17 to play professionally. I assume that most GM’s are professional players or were at some point.

My ranking is comparable to yours having played casually for 8 years, into my 40s. 

I’ve attended a chess club in the largest city in a county of about a half of a million people. There have been club champions. I don’t recall that there was ever a GM in attendance or in competition there. It’s a rare achievement.

You sound like a very competitive club level player who can enjoy and excel at the game even if you can’t quite make a living at it.

After 2500, most puzzles are a pretty similar level of toughness, I don’t think you can get to gm level by just doing puzzles and no coaching tho

Puzzle rating on chess.com barely has useful meaning, it indicates how much time you have spent on puzzles (quantity) rather than your progress in chess (quality)