Hi,
I don't understand what you want to do.
An order can have several products. So I don't know what you want to display in that column ? The first product_id ? All of them ?
On top of that, the products data of the order is not loaded on orders listings, so it won't be so easy to do...
Regarding the custom fields, I don't see either what you're trying to do ? Why to do want to display dropdowns after the total price ? What kind of custom fields do you want to display ? Why allow the user to change his order data on the orders listing and not just display him values ?
Again, displaying custom fields dropdowns here won't be easy and even if you do it, there won't be anything server side to get the data selected so it wouldn't do anything. That would then require to hack in the code of the controller to handle the saving of the selection of the dropdown.
If you're not a developer, it's going to be quite hard and if you are, you shouldn't need to ask what to do. So in any case, I would tell you that you should see that with a third party developer.