Thanks for the videos they really helped explain your problem. I think instead of using px for padding/margin of the parent container which px is the only allowed option right now, use % based div spacer for vertical alignment. Use the same value for both line-height and font-size and then since you are using px based rule for the default layout, base your % off of that. For example, if the container is 200px in height and your font is 150px the difference is 25% X .5 for the top padding…which is 12.5% but since you can’y apply that to the container padding, add a div block above the text, give it a class and set its height to 12.5%. Haven’t proven this theory but its a thought.
playing around, give this a try - http://helperwebflowcom.webflow.com/