You can add a minimum length for a post to give money in the extension settings.
I also updated the code to the new namespaces in the next-back branch.
composer update antoinefr/flarum-ext-money
php flarum cache:clear
If it doesn't work, try to disable and enable the extension.
When I will have a bit more time, I will add some code to give money to users when they register.
For your 2 other suggestions, it requires more development, and I won't do it now.
By the way, thanks for your ideas ?