I just joined KH so someone please verify my response; it's been awhile since I did this.
But I recall you can turn suexec off in WHM (I believe in Tweak Settings?)
And the easiest way to edit php.ini is to ssh into your server, do a "locate" php.ini (think it may be in /etc) use a good ssh client, I use SecureCRT, make a backup of php.ini and then edit away!
Not sure exactly how the reseller hosting works here but I would think that suexec could not be disabled on a single reseller hosting account. As far as the php.ini I am not exactly sure what directives to use to accomplish what you are wanting.
I just ssh'd into my server and did a "whereis" for php.ini. It returned a number of listings and am wondering if someone can tell me if this is THE php.ini file: