The evidence you've mentioned looks good - but only your particular panel can say whether it will be sufficient.
Is he on target for level 5s, or has illness affected the likely results?
No easy answer regarding an EP report, I'm afraid, because one can never be sure just how much weight an individual appeal panel will give any particular bit of evidence. It also depends on the sort of case you want to put forward. An EP report could be used to show:
(a) very high overall ability and suitability for grammar school,
(b) any extenuating circumstances such as dyslexia,
(c) compensating evidence to address underperformance in one area of the 11+.
As an example of (c), if the 11+ happened to consist of VR and maths, and you think the VR result was not really representative of his ability, then an EP report showing very superior verbal comprehension skills would help reinforce the NFER VR score you already have.
On the other hand, if it was in maths that he seems to have 'underperformed', a really good report from the school about ability in maths might be sufficient.