i am getting mostly dmca from USA and hosting in europe
No, there are still a lot of dmca ignore hosting in Netherlands. Dmca policy is depend on provider, not a country.Netherlands is no more dmca ignore now
what about Romania Bulgaria and Switzerland ?
Can I use cotanbo to storege image files and reverse proxy with Offhsore VPS?Well I am not sure but you could store your files on something trusted ( for example AWS ) and use an Off-shore as middle host, when user request the e-book ( download or view ) pull the file from trusted to off-shore.
never hold your files on the same datacenter