The best thing you can do is find a nice open & sunny place with good drainage, plant it in the ground with the root ball just below the surface. Watch this video to see them in full glory.

https://www.youtube.com/watch?v=o5whJ6R-UZ8

Right now, nothing, Acers are deciduous and yours is doing why I would expect it to. Come spring you need to plant out in the ground as per BG's info., but right now it is fine...

I had a Acer in a pot last winter,come spring I planted it in the garden,like Bathgate said and it has done very well.

Put it somewhere out of the wind. They are woodland understorey plants and appreciate a bit of shelter If you can't plant it in the ground it will soon need a bigger tub.

I think the blackened and bleached stems are dead. When it comes into leaf in the spring, you should cut off any dead bits and burn or dispose of them off-site. I suspect there is a fungal infection at work here and removing the affected parts will help prevent it from spreading. I agree that planting the tree out in open ground would benefit it - plant it in semi-shade. Otherwise, you can repot it into a larger pot. Trees in pots need diligent watering. Hope this helps. S.