1) You return SUSPENDED instead of OK from your handler. See also http://svn.apache.org/viewvc?view=revision&revision=1593860

2) You can control all response filters at the byte level with an Output Filter.

3) Hooks already exist for this: https://ci.apache.org/projects/httpd/trunk/doxygen/group__ho...

4) No. Bucket Brigades is the API for this. It's an efficient linked-list of future-data. It's a good API IMO, just needs some understanding, and because its in C, its full of macros (there are more alternatives to making it cleaner if we weren't using C)