I so know what you mean about the worry with glass.
DS used to bang on our upstairs windows so hard it felt like the whole house was vibrating.
They were the most delapidated windows you have ever seen, thin glass and rotten frames, which meant the the glass actually vibrated and moved.
We go so worried that in the end DH covered the bottom 4 foot (we have very large windows) of the windows with hardboard in order to stop DS being able to actually bang the glass.
It stayed like that for over 6 months until we had managed to save enough money to get double glazing installed.
Our house looked like a squat from the outside and it was very embarassing, but we didn't know what else to do.
Reading this thread now makes me a bit mad with SS, as we had telephoned them around this time to ask if DFG's would cover this sort of thing. We were told on 3 seperate occasions, that not only does the DFG's not cover such things as double glazing, but also that ASD isn't the sort of disability that the grants are meant for!
I should of known better really, after all this kind of misinformation seems to happen all the time, but as we have had no contact with SS (which is still the case, school has said we should be getting support, respite etc, but we don't know where to start with this, tbh), I guess hindsight really is a wonderful thing.
I will however count my blessings that the 'family fund' have just given us funding to get a fence put around our back garden to stop DS from escaping, despite this being our second year of applying for a grant with them. They were kind enough to offer to either part fund it this year, or fully fund it now and us not be able to claim again next year, we obviously chose the latter as safety is obviously paramount and the fence needs doing now.