Tony,
Thanks for the extensive description - and congratulations with your upcoming parentship!
I think I understand your explanation, and will certainly try to take the exercise whenever I can again afford to go flying.
One thing still unclear, though: all the altitudes you describe are indeed altitudes, they are read on the altimeter. However we need to know heights AGL - but in an out landing we can only estimate the elevation.
As to the exact AGL altitudes you're correct in saying that this is what they are and what you need. However, when flying anywhere in the world you should always know the elevation of what's below you. You are correct in using your altimeter, which means you'll have to do some public math to change MSL to AGL. A great tool to help is a VFR chart. You can always look at a airport near you and get the elevation of that airport. You can also find a tower on the VFR chart and subtract the Height above the ground from the Height in MSL and this will give you the elevation. Hence public math yet again. This is where your altitude plays a huge key. If you are low on altitude channelizing your attention on things like this has caused a lot of accidents. I feel like what helped save our lives was after analyzing the problem and not being able to remedy the situation I then shifted my focus to saving my crew. My mind shifted to how can I get this aircraft on the ground safely. Mosts part of the country don't change in altitude drastically over a small distance. Not including mountainous terrain. A GPS is also a great tool the Garmin 430 will tell you the elevation of locations near you. I hope this helps.
God bless,
Tony<><