So great to hear you contacted WA, ILT! Well done, give yourself a great big pat on the back/chocolate biscuit/glass of wine for that
As far as the house goes, I'm pretty sure you could prove he's entering the house on a regular basis, perhaps you could set a webcam up to record all day, pointing at the front door on the hall table or somesuch.
That, and if your neighbours are in during the day you could ask them to keep an eye out for you. Maybe you could check with your solicitor and ask her what constitutes evidence for this?
I really think it's important that you establish some boundaries here and stop him coming in willy nilly, it's just unacceptable for an abused woman to feel her abuser could enter her supposed place of safety at any minute.
I still think you should ignore the solicitor and change the locks. Or speak to a more devious solicitor. Especially as he's got a public image he doesn't want to tarnish, so you know he wont kick up a fuss on your doorstep. Did the solicitor tell you what could happen if you did change the locks? If it's just that he can apply through the courts to get a key, I'd do it. Just as a delaying tactic. Find out, and weigh up the pros and cons.
I guarantee you he wont be able to prove he's paid for most of the stuff he's taking. The onus is on him to prove it, possesion being nine tenths of the law and all.
Perhaps you have lost some of his paperwork like old receipts? You might have accidentally on purpose lost them, so he will have a hard time proving these things belong to him, right? Oh and any other paperwork that might be useful to him too, that probably got lost as well, didn't it?
Also, you might want to keep important/precious docs and belongings at a trusted friend or relatives house until you can be sure he wont be coming back to take your stuff. If there's no-one you feel safe leaving this stuff with, then rent some storage for the belongings and keep the paperwork at work for easy access.
As joint owner aren't you able to force the issue wrt to the price on your property? I'm a renter, so am not really up on these things, but surely you have more rights than his way or the highway?
Seriously, though I think you should find a better lawyer. The more I think about this, the more I realise that a good lawyer should've suggested stuff like this to you already. Find a divorced divorce lawyer. My dad and stepmum are both lawyers, and as you can imagine, did very well from their divorces. Nothing like personal experience to sharpen a professional skill.
If he's worried about his image then all you have to do to avoid a proper blow out when you really stand up to him is to make sure he always meets you in public with witnesses. This is difficult to arrange right now, because you need to sort out the house thing. But when you do, just make sure you're never alone with him, or always within sight of the general public. This public image is a great advantage to you, use it.
I'm glad you're not going to retract the letter, I'm glad you're not backing down on the truth.
Who amongst your friends and family know everything that is happening/ has happened? Have you told them? You need to reach out and get IRL support. Abuse feeds on silence, grows in darkness. Speak out so your burden will be lifted a little, and he will find it much harder to abuse you.