Part of the reason it was cancelled was because Iran was still funding a bunch of proxy armies and still developing non-nuclear ballistic missiles?

Even if Iran were arming regional proxies, that's an Israel problem, not an america problem. Though AIPAC et el makes sure no american is ever aware of that distinction.

The US was angry Iran had a civilian rocket program?

That doesn't seem like a good reason to cancel the only thing stopping them from developing nukes. Of course they fund proxy armies, but that's a reginal problem that can be addressed through conventional means.

Cancelling the Joint Agreement is a case of cutting off your nose to spite your face. In particular, it was clearly an expression of Trump's animus to Obama.

For sure part of it is goading them into looking like the bad guys.

Otoh, ballistic missiles eventually become a western europe/NATO security issue.

Not exactly sure how close Iran would be to that, but that is an element of the situation.

Ballistic missiles are a problem but also why it would be better to keep them from having nuclear bombs to put on those missiles.

Yep, the JCPOA was canceled because 1) Bibi has always wanted to go to war with Iran, and knew very well how to get the US's help to do it, and 2) Trump's ego can be trivially played by just saying it's something Obama got credit for.

So you agree they were not exploring nuclear weapons with that agreement in place?

The main reason it was canceled is because Donald Trump is a petulant child and he wanted to erase all of Obama’s accomplishments.