Sounds to me like you may have a larger model. If this the case, it can often be difficult to get ‘everything in your scene’. In your first message, you mentioned that you have to zoom extents to get everything to fit. We’ve had to do this as well, but there’s an easy fix.
Once you zoom extents on your scene, get it to appear how you want it to appear then select all corresponding scenes (LIGHT, HEAVY, HATCH A, HATCH B) and head to your scenes. Right-click and select ‘Update Scene’, then make sure you only check ‘Camera Location’ as the property to update. This will make it so your drawings are all in view, and make it a bit easier when importing into LayOut.
In regards to your retaining wall, I guess I would need to see the model or screenshot to fully understand your question. You can certainly do a split-level representation, and that might make sense if it passes between to standard levels that you need to draw distinction between. Sorry I can’t be more help here.