Java SE (Java Platform, Standard Edition)

Hello I have few questions and problems with Java in Ubuntu:
1) OpenJDK doesn't work with all java applications!

For example: Java Web Start doesn't work with o3space plugin for openoffice.
Applets doesn't work here: http://java.sun.com/developer/technicalArticles/Programming/sprintf/

That is why I installed jre and jdk from sun.com directly, and sun java works fine! But I can not set up it by default. I suppose that I need to set up updates-java-alternative, but it wants file like .jdk.jinfo
How to create that file and use sun java by default?

sun-java6-* packages also corrupted or not full, for example there are no javaws :(

2) When I installed SUN SDK I saw folder named jre. Does it mean that I do not need to use original 18mb JRE from java.net?
3) In original JRE I didn't find any javaws for java web start, is is correct?
4) How to configure Firefox for using sun java, which I installed from sun.com?

Please help, I am confused with all these jre, jdk, openjdk, sdk, gcj etc...