Structural modeling in Generic Family

[ramaji]

I'm trying to model a parametric simple unit in Revit. So, I decided t use the generic family template. I want to model a rectangular unit with exterior wooden wall and interior steel frame. I have three problems
1- I have imported structural column profile into the family, but my problem is that I cannot align the section to two reference line. For example, I want to align the top of the column to the top exterior wall, and align the left side of the column to the left exterior wall; but I can just assign of these sides.
2- I've imported structural framing family in my generic model, but I cannot assign a parameter to the length of the beam, and the length is constant, and I can change the length just in 3D view. Do you know how to assign a parameter to the length?
3-I couldn't use the predefined walls it the family, so, I used extrusion. But I couldn't use the Revit windows family on the extrusion walls. Is there any way to use the predefined wall systems in Revit to be able to use the windows families?
Here is the picture of my model:

I'll appreciate if somebody help me on these.

[Alfredo_Medina]

I posted a reply to this question in Revitforum.org ; I am pasting the same reply here, for reference:

Maybe you should be using a project file for this assembly, not the family editor, because you are saying that you need this "family" to be made of walls, windows, and structural members. Walls and windows are system families. Structural members are difficult to handle as nested families. Therefore, it is not a a good idea to do this as a family. In a project, you won't have parameters, but you will have grid lines, levels, and constraints. If you need different variations of this, you could create a group. Different sizes would be different versions of the group.