I am an experienced assessment coordinator - the example statements you gave, and the example actions are not allowed under any circumstances whatsoever.
I work in a school where socio-economic conditions are difficult, there s very high mobility and where we have high numbers of EAL and SEN children. None of it makes what you say right. Our school also works hard to teach all our children to read - what a bizarre thing to say - and it staggers me that someone with so much experience can make the kind of posts you have been making. And it annoys me also that the playing field is not even because schools like yours bend the rules and cheat.
To then try to retract it in part by saying your children have 'special circumstances' is just rubbish - why post to someone looking for general advice then - not that this matters, since there are no circumstances where you would be allowed to do/say the things you describe.
Our team of readers has been reading for practise SATs for the last term - this was an important part of the process as the school need to prove that Readers make a difference to a child.
This is garbage. Schools have to prove that the pupils taking a test regularly have reading support in the classroom. Either the school is putting readers in the classroom for one term only, just to satisfy the rules - a highly suspect practice in itself - or you mean that they have read for practice SATs. Either is distinctly hooky.
The guidance also states that a reader must be used on a one-to-one basis only. In most cases, this will apply to pupils whose reading age is much lower than their actual age (as a guide, a reading age of nine or lower). Readers must not be used with pupils who are capable of reading the test materials on their own.
Why are a third of your children not capable of this? We have all the difficulties you describe, but don't have a third of children who regularly have to be read to as normal classroom practice, are working from a level 3 to 5 but yet don't have a reading age of 9. 
From the guidance again A pupil may need more than single words or sentences read to them. Some pupils? identified needs, for example their individual education plan, will show that they need the whole question paper read to them so that they can access the test. In this case, schools should administer the test to the pupil in a separate room.
From the amount of reading you describe, your reader children all need more than single words read to them, so all need to be in separate rooms - how do you find the space?
You said Also, keeping the child on track is a key part of the task. Here, you are confusing the role of a reader with the role of a prompter - a separate role. The rules for prompters are also very clear: Prompters should only be used to draw a pupil?s attention back to the task ? not to advise the pupil on which questions to do, when to move on to the next question or the order in which to attempt questions. Ideally, the prompter should be the pupil?s own learning support assistant, so that they know the pupil is not, for example, simply looking away from the paper while thinking.
Your post of "Shall I read the next question now? clearly breaches those guidelines, and this statement there are ways at this point that you can assist, eg. hesitate on a page and ask if child is happy with their responses, or quickly turn over to the next page if answers are good displays blatant out and out cheating, and if I knew which school you were at I wouldn't hesitate to report you.
Yes, you only encourage a student to move on if they have lost focus - a number of our students have issues with Attention and need to be reminded to focus - this is the point of readers!
No, it isn't. The point of a reader is to read, as described in the guidance, and the point of a prompter is to prompt - although not tell them when to move on to the next question.