I would be very wary about directly editing the manifest.xml file. It is very easy to introduce errors. If the SCORM package was published correctly (e.g. for both Flash and html 5), then there should be an index_lms.html file in the package that selects Flash or html 5 based on the browser capability.
Your manifext.xml file already references index_lms.html in the resource section (bold is my emphasis):
<resource identifier="__6QJLTuCcz8u_course_id_RES" type="webcontent" href="index_lms.html" adlcp:scormtype="sco">
It is the index_lms.html file that determines whether Flash or html 5 is launched first. Most content creation programs let you select html 5 with Flash fallback. That means html 5 will be launched unless the browser does not support html5. Then it launches Flash.
There is a line in the index_lms.html file that specifies the order of html 5 and Flash:
var settings = {
runtimeOrder: [{"type":"html5","url":"index_lms_html5.html"},{"type":"flash","url":"index_lms_flash.html"}]
};
If the runtimeOrder parameters are switched (i.e. {"type":"flash", ...} occurs first, then flash will be launched first. In that case I suggest ensuring the the parameters are as shown above (html 5 type is first).
But, be aware that directly editing any of these files may result in breaking the code and the way in which the SCORM package plays. I take no responsibility for what might happen if you follow my suggestions - they are not foolproof and may cause errors.