Question

1. At the pro-wrestling match, the wrestler beat his opponent with his heading.

2. At the pro-wrestling match, the wrestler defeated his opponent with his heading.

3. At the pro-wrestling match, the wrestler beat his opponent with his headbutting.

4. At the pro-wrestling match, the wrestler headbutted his opponent in the ring.
[Which ones are grammatical? Do you have better expressions?]

Answer 1

Instead of "heading," you should use use "headgear."
https://www.google.com/search?q=wrestling+headgear&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi039SE6InZAhXBq1kKHQsjAM0Q_AUICygC&biw=1437&bih=716

If you make that change, 1 and 2 are correct.

In 3 and 4, the word should be spelled "head-butt" (with the hyphen): https://dictionary.cambridge.org/us/dictionary/english/head-butt

I'd re-write them a bit --

3. At the pro-wrestling match, the wrestler beat his opponent by head-butting.

4. At the pro-wrestling match, the wrestler head-butted his opponent in the ring.