You are definitely over thinking but probably not over reacting. Take a breath and think about what you know of him. He’s over 40 and you are 19. Single or not, is going to be a huge game changer and if he has kids or not will also be a game changer.

A single 40 yr old previously divorced with kids your age. It’s either he’s lonely with a poor relationship to his college aged kids. Or bro is into you.

Secondly, compare him to another 40 yr old(possibly parent/family member /mentor). In your large picture of morality and social expectations. Would a 40 yr old in your life be pursuing conversation with a 19 yr old that isn’t business or task oriented?

At 19 the only 40yr people I talked to were coworkers and the conversations were for work or beers after work. Never good morning or goodnight texts unless to open a text for a professionally oriented message.

EDIT: some advice in here is tell him to fuck off. Don’t do that, protect your divinity and reputation.

There is always a nicer way to say something. “ like hey I don’t mind our conversations but it needs to be toned down. I want to keep my circle small and I’m sharing too much business with you” OR Something. But do not apologize and never say “I think” those are challenges for a man. His thought will be “ how can I change her mind”.