This seems to work:
.mktoFormRow.checklist-wrap > div > div > div > label {
position: absolute;
height: 100%;
}
It looks like only the first checkbox has the Instruction text setup on the parent div as a title attribute. The others for some reason do not have the title attribute on the ".mktoLogicalField" div. I spun up a quick test form to check this out and included a few checkbox fields with different Instruction text and was able to see those in Chrome when I hovered over each label and/or checkbox -- as far as I know this should be native functionality.
Any ideas why the other checkbox parent containers wouldn't have a title="" attribute on that div? That should be populated if the Instruction field is filled out on each of the checkbox fields.
I also tried using a checkboxes field type with multiple entries, but you only get one "Instructions" input for the entire field so it shows up the same on all of the checkboxes.
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UPDATE:
I tinkered around in the inspector a bit with the CSS and was able to add some styles to the CSS you've already got going on your stylesheet for the form labels.
I've changed the "min-height:0" rule to "min-height:2em;" (2 elastic measure = 2x font-size tall) to get the label elements to line up a bit better and highlighted them with green and red borders so it's easier to see what's going on here.
The green stuff is the nested label that you'll need to hover over to get the Instruction text on your checkbox field. The red boxes are the "text" portion of the label (not the hover text) for reference.
To distinguish the field labels (.mktoLabel) from the "not" field labels (i.e. the hover text label) I've used the ":not" selector [label:not(.mktoLabel)]. @Jay, this might be helpful rather than targeting the nested div > div > div... in the CSS selector.
This does not solve the issue with the other labels not showing up, but that might be because for some reason the title attribute isn't making onto the parent div.
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