Larch - bigger pot or better soil?

Hope someone can advise... my little larch has limped through this year a little. I followed some online advice early in the year and cut back harsh to promote backbudding, but none appeared until after it had lost its leaves in early autumn and I had tidied it up - it has now sent out some lame new shoots (its almost winter in UK). Most of the year it just sat semi dormant with lacklustre greenery - possible a bit of heat scorching too.
While I love this pot its in and it suits it, I worry that the small pot is not holding enough water or nutrients. Its currently in a free draining mix - perhaps if I added 10-20% organic to hold moisture and nutrients next year it could stay in same pot? Or do you think it needs a bigger pot?
Picture not showing - trying smaller file size...

Personally, I don't like the combination of the pot and tree.
The tree should be more to the right but there's no space for that. I'd like a wider pot, so you have more pot-space on the left side of the tree.

Thanks Auk - good points. Might try and find a similarly textured oval for next year... that would give it more nutrients and a better overall balanced look.

Something like this, maybe?

Thanks - clever, and yes that’s it!