Tested with r43088. Issue 1 is resolved however issue 2 still remains. Checkbox buttons inside a group are not visible when inside h:dataTable, ace:dataTable or ui:repeat.
Test app located at:
http://dev.icesoft.com/svn/repo/qa/trunk/Regression-Icefaces4/Sparkle/Nightly/buttonGroup

For this, you'll have to modify the test app, since it is programmed not to show any label when the button is unchecked. Just remove that condition or dynamically change the label when it's unchecked.

Basically, the changes made were thinking of the standard case where we render the checkbox icons. When using a label, it is only displayed when the button is checked. So when the button is not checked, it presents no visual cues. Some possible solutions would be to render the label with a lighter shade of gray when not checked, or the unchecked box icon.

Why wouldn't we want the label rendered all the time, not just when it's selected?

Ok, this is actually not the case. That's what I thought when I used QA's app. The label is always rendered. What happens is that in the QA app, in a number of tests, the pages are programmed not to render any labels when the button is unchecked. See my previous comment.

QA test applications now updated and buttons are now visible when in a non-selected state. Thanks Art.
All issues verified ICEfaces 4 trunk r43088. Tomcat 7, IE, 11, FF 33, Chrome 38.