Bars at Start and End of rebar group, spacing, and other rebar questions

So I have gotten rebar into revit but now I have a few questions about perfecting the finer points. One problem I am having is the vertical bars should end at the top and bottom bars. The second is I’m not understanding how the spacing is working. If possible I’d like it to be just a distance like 10" not a set number or whatever the spacing tool is creating. And finally whenever I finish placing rebar in the walls and want to move onto another selection the previously created wall rebar is deleted. Is there a way to make dynamo recognize that I have moved on to a new group of rebar without deleting the old?