Will I be able to take it without having to throw it away? Do they measure on ounces or milliliters? its a 5oz bottle (not all the way full -used-) and it has 15ml and the requirements are 3.4oz and 100ml.
No. The rules are crystal clear. They are not in the business of measuring how much liquid you have, they judge based on the container. Even when it's crystal clear there is extremely little liquid they will demand throwing it away if it's in a too large container like a sip on the bottom of a water bottle.
Edit: as a rule maker, if your goal is to regulate liquids this is the only rule that makes sense. I am not saying the liquid rule makes sense I am just saying if your job is to make a rule then the only sane way is by container not contents.