Stunted branches on malus Red Sentinel
I am new to this site, and am hoping to pick some expert brains!
I have just bought a malus Red Sentinel from a local nursery, which I was planning to plant as a specimen tree - photo attached (ignore the Prunus behind to the left). I only realised once it was delivered that the branches have grown very unevenly. There are three in a row on one side (right in the photo) which are v. stunted, though branches below them and above them are longer. The other branches don't exactly look very shapely, either. My question is: will the branches stay like this, or will they grow in time? In other words, should I complain or go ahead and plant?
The pot it's in is 11" dia and 9" high. The tree is 2m high. The nursery said they grew it themselves, as opposed to another Red Sentinel from a well-known tree nursery, which interestingly was of similar height but had a thinner trunk, so possibly younger, despite being same height (and which I now wish I'd bought instead).
My next question is: I have read in one esteemed famous gardener's book that Malus Red Sentinel can be grown in a patio container rather than planted in the ground. Is this viable? If so, could I do this, leaving space for a different tree as the specimen - I was thinking of a Crataegus Crimson Cloud. (I have clay soil and the position would be full sun in summer, partial shade the rest of the year.)
Please forgive my ignorance - I am a rookie!
Thank you in advance.