I am so sorry to hear about the problems you are having. It is not uncommon, I am sorry to say. There are too many people out there who just make a fast buck out of the 11+.
If you have the time and patience, and your DS will work well for you, then continue to use materials from this site to help him prepare. Use the various materials in the order that Patricia has recommended:
:: Susan Daughtrey Bright Sparks
The Tutors CDs are very useful as fillers and for dealing with any specific problem types (other than Codes, for which pen and pencil is essential), as are the IPS daily tests.
I would agree with andyb that you would be in a very good position to pull out of the tuition and ask for a refund. The silence from the other side is rather telling on that front. Any legal eagles out there who can tell Sara what the equivalent of the Sale of Goods Act is for this situation?
An alternative, if you are short of time, would be to continue with the tuition through gritted teeth and make sure that your DS is only focussing on the 21 types. Also check the homework material yourself before he starts.
A reasonable practice schedule would be 2 hours a week, including tuition. I am doing more with my DS, but he does love doing puzzles, so it is not a problem for him.
We are doing 1 hour of tuition (from a tutor) plus 2 papers a week at present. We will go up to 4 papers a week in the hols, although only IPS daily papers when we are actually on holiday - and I suspect that may not happen very regularly! Patricia thinks I am a complete slave-driver at that level.
Be very careful not to get to "burn-out" though. If he seems to be getting to that point, give him a break (and tell him so) for a week, and then start back in gently with the CDs.
I am being very much more "hands-on" with DS2, having relied on the supposedly amazing tutor the first time round. After each practice session/paper I go through and check the answers, and I keep notes of which types have been answered wrongly. That is building up a picture of where he is finding it harder, and I can then deal with those types specifically.
Very good luck