Isn't a probe suppost to tell all the research, defenses and ships on a planet when you get it to level 8? I have it to level 8, but when ever I Probe someone, it just says how much they have in resources.

No, the information listed in the Espionage menu is talking about incoming attacks to YOUR planet. Defensive Espionage, basically.

When you probe someone, the amount of information gathered from 1 probe is based on your opponents tech. The higher it is, the more probes you'll need to send. The lower, the less you have to send.

Oh. Ok. Thanks

You can set the number of probes you want to send at a time in the options menu (in the sidebar), unless you want to leave it defaulted at one probe and send more at a time manually.