I’m sorry to hear you have lost your husband and I can understand why this is hard.
But you’ve made a mistake not having a written contract and ideally you should get one agreed and signed now , although there’s not a lot you can do if he refuses. Yes technically there is a verbal contact but good luck if you have to rely on that.
Legallly a lodger shares common spaces with you - I’m guessing that’s only the kitchen , as he has his own bathroom and living room . He has as much right as you to use the kitchen if that’s what you have agreed - he doesn’t need to ask you the same as you don’t need ask him. You can’t tell him it’s not his space too.
what have you agreed about the cleaning of shared spaces - do you have a cleaner ?
Is there a dining table and chairs in his living room and in yours ? That might encourage both of you to eat your meals in there and not in the kitchen.
If you and your lodger DONT share common spaces and his place is self contained then he’s a tenant and you are in a whole other legal situation, he has rights of tenure and you need to pay income tax on the rent etc . So it’s not just a technical difference , it’s really important about shared common spaces, it’s one aspect of being a lodger ( as is providing other service like cleaning or laundry , which is why I ask ).
You need to register him for council tax and on the electoral roll at your address - yes that’s your job as the householder . Of course you can no longer claim any single adult discount ( if you have been doing so ) .
You may need to tell your mortgage company - Check your loan agreement very carefully as you REALLY dont want to breach this.
You will also need to tell your house insurers and take out landlord insurance (Id get legal cover too).
Im afraid you need to be a lot more business like about this - he’s your paying customer not someone you are doing a favour for. I say this as someone who has had lodgers for years .
Give yourself a few months to see if it’s working for you - it’s too soon to tell yet. As Pp have said, it’s mostly down to your lack of clear communication with him.
I know it’s hard to adjust your expectations but hopefully it can be sorted out to your mutual benefit.