Interesting spell,
It won't be used often however because of the Concentration duration.
I would suggest maybe change it for a duration of 1 minute (like shillelagh), no need to keep concentration.
Just add that somewhere and you're golden : The spell ends if you cast it again.
Also, I would...
This is a intriguing thread, and a potential great resource for DMs like me who like to produce homebrew.
It is somehow a functionnal first throw, and has a lot of potential. I'd like to encourage you to polish that little gem of a system further.
Thanks sharing your ideas, this is the reason...