pickup or ship option in checkout

I am not having much luck trying to get the new field to display on my product detail page.

I have added the field of products_weight_display to the products table as a field to display the actual weight of the product, so that I can put the shipping cost in the products_weight field for shipping purposes.

Can someone help with getting a newly added field to display?

There seems to be a bit of a hicup with this approach.

Whenever someone changes the quantity in the shopping cart, the shipping remains the same.

For example Product A cost $5.00 and has a shipping cost of $1.00.

The customer adds Product A to their shopping cart, and then in the shopping cart changes the quantity to 2.

When they checkout it shows

2x Product A $10.00
Shipping $1.00
Subtotal $11.00

When it should show

2x Product A $10.00
Shipping $2.00
Subtotal $12.00

This also happens when someone originally has 2 items and changes it to 1, they are still charged shipping for 2 items.

How can I fix this?