One of the other common names of Himalayan cedar is California Christmas tree. By far the most impressive ones I've seen were a row in front of the state capitol building in Sacramento. These were planted in 1871. One of them measured 101' by 17' 9" (approximately 5 1/2' thick) during 1989. What you are seeing as "beautiful" is the foliage of the young small tree above the ghastly stripping of most of the trunk, which served primarily to make it look odd. If it was furnished with branches to the ground it would look 10 times better. https://losangelesloveaffair.wordpress.com/2011/11/25/114-deodar-trees/

Plant of the Month: June 2002 - Banana Shrub; Michelia Figo http://www.arthurleej.com/p-o-m-Jun02.html

Yes, remove it. It is not a valuable tree - it's basically a throwaway in the nursery industry. All prunus are susceptible, some significantly more than others. You can treat with a fungicide and a lot of pruning, but I wouldn't bother with a purple leaf plum. If you're looking for a spring flowering tree, consider service berry (amelanchier)

I'm don't know the answer -- I've always just seen them labelled Virginia bluebells -- but I do see what you're talking about re: leaves. Is it possible the foliage on the shorter, green leaves is simply more recently emerged? The plant does tend to elongate as spring progresses. I would just keep an eye on it and see what it does, I guess.