I'm pretty sure it has to submitted by 1st November, otherwise it won't be accepted.
All of the evidence is submitted together; academic evidence and evidence for why your daughter performed less well than expected.
The head's report is automatically sent to you, and is included in the review, but you can choose not to attach it if you don't feel it's helpful.
I'm very sorry for your loss, but need to ask - did you inform the school before the test? The head is asked if they knew of any reasons for underperformance before the test. As you will have evidence of your loss, then it should be less of a problem than a child whose parents claim they were ill (but didn't tell the school), as the panel are less likely to consider it.
Does your daughter go to a Bucks primary school? If so the head's scores for grammar suitability will be important, if she doesn't it holds less sway, as Bucks head's are asked for the ratings before the test (so an objective view), whereas out of county head's will only give the score after, so it can be more subjective
Going for an appeal instead is entirely up to you, and you are correct thst appealing after an unsuccessful review is almost certainly going to fail.
However there are downsides to appealing. If you win an appeal, your daughter won't be deemed qualified for every grammar, as you'd be appealing for an individual school (or schools).
An appeal will also take place after the first (and maybe subsequent) rounds of allocations, which means the school may be full, and therefore hard to gain a place.
If your daughter has been working at GDS and you have a few years of evidence to back this up, then a SR may be a better bet, but you'll need to act fast.
You may be able to submit the application and add the head's form later.
What was your daughter's score?