I don't think that any of us can tell you what it might do to your chest specifically as we have nothing to go on. With the measurements you gave, it's possible to flatten it out by at least a couple of inches. However, it really depends on a number of things - how big your actual moobs are (how much flesh there is to flatten), how broad or skinny you are, etc.
If you have a lot of flesh there, it will be obviously harder to flatten out. It can be done convincingly, even with enormous chests - it's also a matter of choosing clothing that will not be tight against the chest, too. Sometimes larger guys will have a "lump" in the center which is the flesh being squished into a monomoob basically. Regardless, it's impossible to tell most of the time if you choose the wardrobe correctly.
As to whether a binder can squish you as flat as you can squish yourself with your hands - again, it depends on the amount of flesh and the binder you're looking at.
