Maladministration - DLA claim

My wife has been royally messed around by the DWP related to her DLA claim.

Up until April 2010 she had been awarded Higher Rate Mobility and Lower Rate Care .
When asked to reapply in 2010 they wrote back advising (without detail) that "whilst your answers on the form are largely similar to your previous application we feel the previous award was incorrect".
This was obviously concerning so we wrote in asking them to look at the decision again, and to contact her (then) consultant and GP for further information on her condition.

They did half this request - wrote to one consultant treating only one small subset of her symptoms who advised that those symptoms shouldn't be too debilitating.
They received this and the following day advised that she was no longer entitled to any DLA at all.

We wrote in again (late due to her being in hospital) with a lot more info advising with examples exactly why their previous decision was incorrect, and asking again for them to contact her GP as the only one who could cover all her symptoms.
They wrote back about 6 weeks later advising that they were sorry for the delay but they were awaiting a report from her GP. THey never requested one and in the end just wrote back upholding the previous decision and advising that they didn't accept her request for a late appeal.

In November last year we wrote a formal complaint about the handling of her application. We received no response at all. We spoke to our MP who chased them and magically a letter had been sent and must have been lost in the post. We got a copy of this letter which didn't address any of the details of the complaint, so wrote back.

This time we got a letter back from Terry Moran (top dog at DWP it seems) advising that htey're under no obligation to contact anyone and that if we wanted her GP's evidence to be heard we should provide it. He ignored the rest of the formal complaint, and seemingly didn't think the fact they'd said in writing that they were contacting the GP was anything to apologise for.
As part of the formal complaint we asked them to reconsider their decision.

In the last week of December we got 2 letters, 2 days apart. One advising that they couldn't look at her claim again as it was too late. The other advising her claim was being looked at again and we should hear something in around 11 weeks.

In January querying the two letters we were advised that they had no record of the second letter.

We did a SAR to get all the info from their records - we'd lost a letter or two over the years and wanted to make sure we had the full file to (yet again) formally appeal.
We were stunned when the SAR pack came through quite how much was missing. Basically all the letters that show them screwing things up (the we're contacting your GP letter, two letters from December, half the decision maker paperwork) were missed out. We have copies of these luckily.

We've now been waiting 3 weeks since sending in all the details for a full appeal and we stated the lost post & delayed response from Terry Moran as the reason for the appeal being late.

I realise this has become a bit of a long post - but essentially I'm after some guidance on these points:

1) Is it unusual to have no confirmation of an appeal form being recevied after 3 weeks?

2) Is it common for the DWP to not provide all information with a SAR??

3) Aside from the DWP guide on complaints about maladministration, is there any more info out there - particularly on any successful claims?

I genuinely feel that my wife has suffered as a result of not having a diagnosis for so long. She first became ill in 2007 and it was only last December that her condition was diagnosed as Fibromyalgia with some possible underlying neruological conditions.
In this time I've seen her go from a fit young lady to someone needing two walking sticks or a wheelchair to move as short a distance as across a room. It is puzzling to her doctors, friends and family that the DWP wont give her DLA - but it seems like they're going out of their way to only seek the evidence that suits them.