Good work with kindle import
I had to apt-get install python-tk but the plugin told me that so not an issue
spliting at chapters is pretty easy really
find
<blockquote>
<span class="rule_9"
replace
<hr class="sigil_split_marker" />
<blockquote>
<span class="rule_9"
replace all , job done. your book may vary.
but you just need to find what the start of a chapter looks like.