Ok, some of problems has been partially solved:
1) It seems that is a real problem only on Linux. Under Windows Tomcat 6.0 can log error messages to one of its log files. I didn't manage to get that on Linux, though.
3) It's not about declaring in components.xml or by annotations as I initially thought but about keeping components in main classloader, not hot classloader where they are not visible. So there is no possibility of hot deployment under Tomcat I guess?