Sub 1300 that's my rating in the singular official tournament I participated at.

But given how easily I can crush them and how often they want to make illegal moves (btw above bench seems to use a harness that pokea the model until it gives valid moves).

I would rate them around 500-800 big range but at that level it's all about if the model can recall an opening or not. If it plays good first 4-8 moves the person on the end will fumble for certain and they win.

I can play good/best moves till 14-15 moves if I remember the lines and find someone who falls for it.

If you could give them the lines as prompts like the best 20-30 openings then they will be around 700-800.

700 is around the rating for a human who doesn't know the tricks but can do bare minimum calculations and understands the rules thoroughly.