I just joined, went to My Settings and added . If I hit save changes(which it already showed a photo near top) I got the same error message but the profile phone and avatar were there when I tried a post or viewed my already posted messages so you may want to check that.
As far as resizing, just open up Paint on your computer and click Resize, you can choose percentage or pixels. Select pixels and make sure both are less than 200. One number will generally auto fill to keep your picture right. If you can't figure it out post the picture you want and I will resize it and upload so you can save and then upload it that way. =)
Oh and near the bottom(once you have added a picture to Paint) it will say how many pixels it is as well as the size. I took one of my husky puppy photos and cropped the part I wanted to use for profile picture, then I resized it so I could use it.
Looks like you got it done but in case it helps someone else I'll leave my other messages. =) That is a beautiful betta!