I don't really know the FOMO site you are referring to, but if you can still withdraw your assets there, you should withdraw now. to be honest I would rather hold ethereum than investing in something like that. as far as I know, you might be able to use the 4 eth you have to invest in other, more reliable places. there might be a way to get out of your situation, but it's quite difficult and risky.
I dont understand people who would rather invest in something sketchy instead of more solid investment - then lost some funds - and then be surprised and complain about.
Like - what were you thinking about, it is a high risk investment