1. The newest version of MultiMan doesn't do diskless support. You'll need a version that doesn't use syscall 36. Check the OP in the MultiMan thread for a full changelog and to know what version to install. You can install Rogero's 7.8 and use it in conjunction with lv2 patcher, as I know that version still has diskless.
2. PS Jailbreak Compatibility List - Home for a compatibility list.