1&2) There was no retcon to establish the Phoenix Force keeping Mesmero from raping Jean. All Classic X-Men #17 did was fill in the gaps as to what happened prior to the event of the X-Men being presented as carnival side shows. The issue clearly established Mesmero not to be a match for the Phoenix, which completely blows your argument that he can take control of a Phoenix Force character without the element of surprise.
3) So, again, you are making that up about Rachel being vulnerable to mind control because of her hound days because nothing in canon has stated that.
4) I believe it was one of the later issues of the Official Handbook that stated something like he was born from the first nightmare. If he made that comment in canon, though, it would be fact.
5/6/7) I'm not fabricating anything. The issue made it clear that Rachel was putting herself in danger by maintaining the global scan effort.
8) You are overplaying Rachel, hence she doesn't stack up well to other telepaths when she is pitted against them.
9) Rachel does not have unlimited potential on her own. Let's look at her fight with Selene in Uncanny X-Men #207:
https://2.bp.blogspot.com/ozR0hL2dTB...Y-mYvSPi=s1600
Selene: "I knew she possessed awesome potential, but I never dreamed it would be so quickly realized."
In this story, Rachel being Phoenix was the potential Selene was referring to.
Here are the rest of the scans of their fight:
https://2.bp.blogspot.com/f7J8hl7rJ6...arClfJe_=s1600
https://2.bp.blogspot.com/_HHBcIMobF...6WzP5Z0z=s1600
This is before the retcon where the Phoenix Force was established to be a sentient entity all on its own. It was still viewed as being part of Rachel's innate potential, and not a cosmic abstract entity. That later changed to Jean, Rachel, and future psis in the Grey bloodline being able to wield the PF when it became a cosmic being separate from them while only a few others outside the Grey lineage could. In other words, Rachel's potential was hinged on her being able to host the Phoenix Force. This would also explain Emma's comment about Jean being underwhelming as a basic telepath (in other words, without the PF).
So, with that being the case, without the Phoenix Force, Emma>>>Rachel.