Thank you for confirming and apologies for the delay in responding. I will reply in accordance with your numbering:
1. Given that you have now separated, you are within your rights to keep any income you receive in a sole account and you have no obligation to use the joint account. In relation to the amounts in the joint accounts, they are significant and you are both equally able to access it without the permission of the other - there is a risk that this may be used either partly or fully which you can apply to court to have an injunction placed on the account if you believe this will be dissipated unreasonably.
2.Spousal maintenance is in relation to his reasonable needs and, without a court order, you have no legal obligation to provide him any payments. He will need to apply to court for an order.
3. You can continue with any previous plans regarding the property - unless there is an order preventing you from using the funds.
4. The proportion is difficult to confirm without full and frank financial disclosure, but given the long marriage and three children, it is likely that the main carer will have grounds for a higher split of the assets - however, in your case if he has no income or capacity to earn to support himself he can seek spousal maintenance or a higher split of assets in lieu of spousal maintenance.
5. Again this is difficult to confirm as there needs to be disclosure of both your reasonable needs and income and it is usual if the payee has the sufficient resources to pay for the payor's shortfall between their income and reasonable needs.
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