Been a long day at the office, so I haven’t had a chance to catch up on this. I’ll try again tomorrow but in the meantime…
For the first question you will likely need to pull the individual segments from the dimension. I don’t know of a node that does this OOTB, or in any publicly known package. That isn’t to say it doesn’t exist - just that I haven’t come across a need for it so it’s not in my mental rolodex. If you’d like to give it a shot on your own, you can refer to the Python code in this topic: Dimension segments from continuous linear dimension, and pull some other info from the Revit API documentation. Don’t worry if you’re new to this - it’s not too bad of a first task for a Python coding, as a lot of what you need is already out there - just a matter of retyping and assembling the parts you need.
For the second question you can use a List.SortByKey node after the List.GroupByKey method in my post. The list is the Groups output @L3 (might be 2? Hard to lace straight in my head after this day), and the Keys are unique keysoutput set @L1 (99% confident on that list level - pretty much can’t go wrong). I’ll try and have a look tomorrow, but if you get anywhere before then be sure to post it. 