Is the border substantial enough? Or should I add more?
That is beautiful work! But I think maybe you asking this question suggests you're over the border and would welcome permission to leave it as is?
In which case, honestly it does look great like this. If it's not fun, you could totally stop. And let's face it, it's crochet, if you suddenly decide one day that it'd look better with a chonky border you can just attach some new yarn and go for it.