WooCommerce and heating oil sale

Hi there
A little newbie here. So I hope I posted the right place ??

I have a website that sells fuel oil, heating oil and diesel.
The shop part is WooCommerce.

But there are some issues

– Users can not order less than 400L (Liters) and max. 3000L (Liters)
– The product is displayed (per. Liter) – i then multiply up.

I use this feature.
https://docs.woocommerce.com/document/adjust-the-quantity-input-values/
The problem is that the site / price not auto update when i / users raise the volume / liter quantity.

Also, the delivery have a max. limit (for free shipping)
How do I set a rule up for that?

Really Hope you can help me here
Or maybe seen some functions like above.

C yaa | Cheers
Kimo