Leaning to one side can be caused by constipation, but it can also be be due to the dementia itself, especially if Parkinsons is involved. Mum didnt have this, but at her care home I used to see the carers using cushions to keep people upright in their chairs.
Not sitting in the right place is a perception problem. Your wife can see where she wants to sit, but doesnt correctly work out where it is in space. Ive seen this many times - sometimes the chair that someone wants to sit on may be the other side of the room, even though they think it is right in front of them, so they end up sitting down on nothing in the middle of the room, or even on a chair that is already occupied! The best thing is to guide her to the right place and give her simple instructions, so that she sits in the right place.
Im afraid that forgetting how to use things like phones and cutlery is par for the course. I can understand your dilemma with taking her out. Is there something like a dementia hub nearby which caters for people with dementia and would be understanding of their problems? Otherwise, when you go out could you order finger food? Sandwiches, pizza (cut by you into manageable pieces), scampi and chips or cake might work better.
