My suggestion is work out what you want and do that. We do not know your needs and wants or what space you have for growing more trees.
I suspect it will be difficult to create a good bonsai from that long, straight, bare trunk. I suspect this tree has been crowded with other plants in very poor conditions. Bottom branches have all died off from lack of light. It can be very, very difficult to get new shoots on bare pine.
Maybe it was the only JBP available? Maybe it was very cheap? I would have passed that one but I have plenty of access to better trees so my choice is not relevant to you.
I cannot see any use in ground growing this tree. Now you have a tall, straight trunk with no bends and very little taper. After growing in the ground you will have a much thicker, tall, straight trunk with no bends and no taper. Ground growing will thicken trunks but it does not fix problems. Usually the problems are just magnified so even worse.
Getting good bends in that trunk will not be easy, even at only thumb thick. Possible but not easy. I would need to see the surface roots (nebari) before offering suggestions on what might be possible with the trunk as is.
The weeds are competing with your tree roots for nutrients and water. Eliminate the weeds and the tree will be healthier and grow better.
Layering pine is usually considered slow and difficult but it can be done. We've seen others from SE Asia layer JBP easily and successfully so maybe that's your best option.
Just be aware that if the lower trunk has no healthy shoots it may not survive after taking the top off. You should layer above a live branch if you want 2 trees but if you only want the top section that does not matter.
