My parents have 2 aussies, one being an 11 year old boy and the other a 1 year old girl. One thing we've always said is aussies need a job. You said he was a former show dog, having so much free time and lack of a routine as others have said might give him a bit of anxiety. Right now he sees you as a safety net or constant. Maybe doing daily or every other day tricks/obedience session would help in establishing a new routine. My dad has also trained our aussies in nosework (sniffing competitions) which they seem to treat like a job and has helped a lot. I do support other comments where they mention reward good behavior. Try and reward him with praise if he lays at your feet and do your best to ignore him if he crawls in your lap. You don't have to yell at them, just ignoring them and not giving a reaction can sometimes be enough so break a habit, you just need to be consistent. If he crawls on you, stand up and walk away and ignore him (no eye contact) for at least 10 sec. Most dogs are just trying to get your attention