But of course they aren't going to wait for your side of the story. You get a booking/sending off, you get a fine and/or a ban. They will only consider it when you appeal. Can you imagine how many bookings there will be throughout all the leagues that come under the Sussex FA. Do you really...
Why should it relate to what his 'pocket money' is. Does he buy his own football boots, training gear etc. I doubt it. So, you have to pay on his behalf (reimburse his club) but surely if you think he was wrong then you might punish him some other way, stop his wi-fi, ground him or something...
So a little jostling escalated with your son raising his hand, presumably threateningly so probably deserved to go off. Did the other boy threaten your son? I suspect not otherwise he would have been sent off as well. As for the fine, whilst the club will pay surely you have a moral duty to...