This tree is a rather healthy nursey grown tree, the growth patterns are consistant with the heading techniques used by nurseries to make a small tree look fuller, thus more desirable to the uninformed consumer.
The belmishes on the leaves are any one of a number of fungal problems and look to be an aesthetic problem only.
When choosing a young tree to plant, I look for something with a single leader or well formed double lead. Your tree has a very tight group of branch unions, this can cause problems long term.
I would probably take the skinny branch in the front out then reduce one of the two big codom stems severly for removal in a year or so.
I would not be too concerned with any other thinning till these concerns are addressed, unless there were one or two quick directional cuts that could be made on sections that are intended for scaffold.
with these I would look at the two brances and long term structure would cause me to decide wihc to go if any. maybe the can be separated and not removed.
it is a shame that the nursery industry is driven to sell what the consumer wants instead of informing them as to waht is best long term.
Now I want a close up of the base of the tree where it meets the ground. Pull the grass away by hand.
post on you page and then link to this site so it shows up in the page.