"Love"to see you struggling too like I did for 15 years...

But just a remark about the "trunk"of the tree:
Looks like an "overkill":
A wooden core AND drilled wire...and as peteski wrote: rather short branches.
After many years I've choosen to use floristic wires as a "core"of the frame of the tree. The wire has a diam. of 1,2 mm. Still a lot smaller than a wooden dowel or small wooden twig from outside...Besides that it works more /a lot easier/less difficult when using a core of smooth floristic wire!( see attaches picture)
WHEN using a real twig, like the ones from buxes sempervirens, I drill smal holes in it( about 0,5 -0,8 mm) and add drilled branches( actualy small trees) made also from floristic 0,35 mm diam wires and glue these "branches" with a drop of superglue/CA into the holes made in the twig of the Buxus sempervirens.( attached picture)
Mostly I use this technique for big older deciduous trees.( last att. picture)
Jos