You said morning sun - how much? Maybe hostas would be nice. I feel like you need something with bigger leaves for contrasting texture. You could get a variety with variegated leaves to give you a little color, too.

The wall looks very well done, but it looks contrived, forced, and unnecessary. If you keep it, I'd definitely plant a thick ground cover in front to help hide it.

Sadly, yes. Someone did a very good job with it but it makes no sense.

The sides cannot match as they are of different depth (after the little wall is gone). As I read your post again I noticed that you want something that is easy to maintain. I was quite surprised because what you have planted so far looks like it needs a lot of grooming. Speaking of grooming, I have never seen a sheared Burning Bush before today. I think you should remove them. You did not have enough space for two anyway.

I see absolutely no reason to remove the wall. It may not have a specific purpose but it does provide a point of interest (even a focal point) and adds some character. I would consider removing some of the foundation shrubs. They are planted too closely (requiring frequent pruning to keep in size) and they look a bit regimented and soldier-like, marching across the front of the house. There is no reason for the two sides to match. That is a more appropriate approach if the house was symmetrical but it's not and attempting to have symmetrical plantings on either side will throw off the balance and make it look forced rather than natural.

You do need color and in front of the wall is ideal space. You could plant with annuals or any suitably sized perennials. I'm not sure how low they have to be, as you have some room for height there.....just keep whatever you pick lower than the wall.