I have only recently started home educating my son, who is 11. He has a lot of Asperger's characteristics, although he is undiagnosed, and he is also dyslexic. So far, we love home education. We feel much closer and he is much easier to deal with now that he is not stressed out by school.
My son starts work at around 9.30, after we have taken my youngest boy to school. He finishes work between 12 and 1pm and the rest of the day is free time for him.
With regard to where to start; I didn't do any 'deschooling'. I chatted with my son about what we should do each day and he wanted to emulate the school timetable because that was what he was used to. So, at first, he started every day with reading, then he did some Maths, then some English. After that, he would do some topic work (I let him choose any subject and he surprised me by wanting to do a topic on fish, which has now evolved into one on 'deep-sea creatures') or cover something else, such as history, with his dad. We are following the National Curriculum for English and Maths, but nothing else.
This worked well, but I have noticed that we are becoming more flexible now. The other morning he really wanted to find out more about what was happening in Japan and to write about it. It seemed ridiculous to tell him he must stick to the routine. After all, that is one of the joys of home education - the flexibility.
We are using BBC Bitesize, which we have found really good. There is a wonderful game on the website called Questionaut. It might be a bit too old for your son, but it has fabulous artwork and music. Both my son and I love it!
Re: the Maths. This week, I have subscribed to Maths Whizz, as Maths is my son's weakest subject and I am not much better. He loves computers, so this has turned out to be a brilliant way for him to learn. It costs £20 a month, which is loads cheaper than a tutor (which I was considering). Like your son, mine is way behind in maths (Maths Whizz assessed him as having the maths age of an eight-year old). However, he is picking up things at home that completely passed him by at school, simply because he learns better one to one, so I hope that he will catch up. As the intention is that he go to secondary school in September, I am aware that he needs to be on a level with his peers, if possible. I don't put any pressure on him about that, though, and he certainly doesn't know where he is in relation to his age. I think the whole age thing is daft, actually, as every child has a different developmental pathway, particularly if they have special needs.
I have a 'home-ed' file and put all my ideas and plans in there. I've noted down any forthcoming events which my son might enjoy, such as a nature festival or a special day out at a farm, and also any ideas as they occur to me (eg a website showing the world's best underwater photos). I have found several freebies, such as a free bird table (collected coupons from bread for this) and a free 'grow-your-own' vegetable box being provided by a local charity. Next week, I'm taking my son on a trip to the London Aquarium as part of his topic work (not cheap, but it's a one off). In addition to using the internet, we also use the library a lot and watch relevant DVDs (such as David Attenborough's 'The Blue Planet').
My only reservations are that my son is not socialising (this was one of the sources of stress at school, so he doesn't want to see anyone except us for the moment) and he is not getting much exercise (he hates organised sport and clubs). However, I hope that, with the weather changing for the better, we can get out more together, if only for country walks.
I feel like this is a precious time for us and I'm really glad that we are having this time together. I hope you have a lovely time with your son too. 