@Dooodoooo please do what DangerMouseisace is advising. Call Social Services. Tell them your grandad has Lewy Body Dementia and you are in crisis (use those exact words). Explain your own health issues - DO NOT PLAY THEM DOWN. Don't say everything is fine or will be you're just a bit down. You are not just a bit down. You need help. Your grandad deserves help. Insist on an emergency care assessment.
When they come tell them you are not able to continue as carer. Don't let them talk you into managing a moment longer.
Don't worry about crying on the phone or in the meeting - they need to see or hear that you are genuinely up to your eyes in stress, medical problems and worrying.
When they come for the assessment don't pretty things up. Leave things messy if that's how grandad is living, leave his bed things on the sofa. They are going to assess how he's living, they are not judging you or him.
My mum has Alzheimer's and went into a home in April. Before that she was in respite following a number of falls at home. In the 5 years before that me and my two sisters cared for her. It was hard enough for us so I am full of admiration for you. I sat in the meeting for my mum with social services. I let mum do the talking - usually I'd 'interpret' for her. So when she was a bit muddled I'd say 'mum means....'. I didn't do that. I let them see just how muddled she was. I stressed time and again that she could not be left alone - she was having more and more falls, had meals on wheels and three carers and we still couldn't manage. I said we were in crisis. Thirty minutes later she was on the list for a care home place.
My mum was housing association. They are not allowed to kick your grandad out as long as his rent is up to date and he is not causing major problems. I'm guessing the woman you spoke to thought you may have been trying to obstruct them. We know you weren't but she's probably heard everything so wanted to reiterate that they can take you to court if you didn't let them in.
Now I am going to say something that may seem as if I am having a go at you. I'm not. I'm saying this as if I were talking to myself two or three years ago based on what I know now.
You are getting walked over because you are allowing it to happen. I allowed it to happen to me. The only way this is going to improve is for you to reach deep down and summon up the person who has had enough. You need to stand strong and say you cannot and will not do any more. This ends. And don't worry about your aunts saying 'you did this' if he ends up in a home. You did do that. You got him to a safe place. If they continue with it just say 'lucky I did because you weren't helping and weren't prepared to' then walk away - let them argue at your back. Turn your phone off. They can call you what they like - only you can allow that to hurt or influence you.
The minute I said to the social worker 'we're in crisis and we cannot look after mum at home any more' I felt 10 stone lighter. Seriously.
Yes, you will have another push to find the right home and you won't have much choice because the social service budget doesn't stretch to luxury. But my mum has no savings so has the basic accommodation and is very happy and cared for. Yes, someone will have to sort all of his things out. But you cannot go on like this. And if your aunt has POA she will have to take up the reins on these things - you don't have permission.
And change the thoughts on your own mum. She'll be looking down saying 'well done, you're doing the best thing for grandad and well done for sticking up for yourself and him'. She would be proud.