I need your help with importing BVH onto model's armature please

Hello fellow Blenders, I need your help.
I finally set up the sensors to record me swinging a stick around. I successfully exported my efforts into a BVH file. I opened Blender and made a low-poly model and created a blank armature rig. I imported the bvh file, after tweaking it on the bvhacker app. I assigned the specific bones from the imported bvh onto the blank rig. Even though the collar bones are pushed back, for the MOST part, it did a good job copying the rotation from the import onto the blank rig, shown here:

So then I went to add the ARMATURE modifier onto the model, assigned bones via weight painting… And it’s coming out to look like this…

I’d really appreciate if you guys take a look at the file and tell me what I did wrong… and what I can do to prevent further mistakes.

Thanks in advance guys!
Here’s the file.

You have unapplied scale. Scale your armatures in edit mode only. You scaled them in object mode. Then when you parent them it will try to maintain scale. Unparent mesh. Clear your transforms Alt S, r, and G on your armatures. Go to edit mode and adjust. Then reparent.