"Next to each task I would like a checkbox, creating a series in a portal; the series of checks are different for each new record.
How do I size the text, or do something so that the boxes neatly align with the text?"
When I read that, I can come up with more than one interpretation. Can you post a more detailed example of this?
"is it possible to create a field next to each check box which records the date that the check is inserted?"
Yes. It could be scripted with a set field step that puts the current date in the field, or you might be able to store an auto-entered modification date if there are no other editable fields in that portal record.