They're plenty strong, I lift boats that way using straps, a gantry crane and a forklift all the time for bottom cleaning and swapping out trailers, unloading new boats brought in by flatbed. I don't advise leaving a full sized boat suspended that way for long periods of time, up to a couple days is okay.
For the bow, run your rope down one side of the bow, through the eye, then up the other side, like a cradle. I do it this way not b/c the eye isn't strong enough, but b/c it stabilizes the boat's bow from being too tippy.