Increment number with multiple cursors

if you press CMD + Option + arrow you increment number by 10
press CMD + Option + Shift + arrow will increment number by 0.1
can't find a way to increment by 1

I don't know in what way this would need to involve multiple cursors. It looks like you intend to use javascript to process this, since you are putting the unique identifiers in the id, but I would use PHP and create a two level array in the name field. With checkboxes, I don't think you can use the same name for the whole group, the way you would with a radio group, but you can certainly use an array with names like checkbox[0] or even checkbox[<?php echo $value ?>]

A lot depends on whether or not you know how many checkboxes you will need. I often have them coming from a database set of records where I don't know how many there will be.

Processing the group means your post data will contain a separate array for the checkbox set.

You need to provide more info about what exactly you are doing. There are too many different ways this could go to give you a definite answer based on what we know now.