Hacking a phone via Apple-ID, what info can be accessed?

If someone knows the answers to my security questions for my Apple-ID what info can he get access to on my phone?

Stored text messages (phone, kik, messenger etc)

Photo stream

activate “find my i-phone”

Could he do this remotely from his own i-phone?

Reason for asking:

Even after I changed my pin code my ex seems to know almost everything about where I’ve been, who I’ve talked to, what I’ve written on kik, mail, which photos I’ve sent etc. It’s possible he could’ve had access to my phone physically (when I was asleep), but it seems he’s been able to monitor what I do on my phone remotely from his own phone during a long period of time. Is that possible?

He knows the answers to my security questions.