I think one thing you will see, as you age, standards change points of importance take a step back and new points arise. Your timing is pretty close I feel to what life changes are going to bring. Soon your focus will shift much more towards smallsteps, (not say she is not a major focus always), but as she grows and real school years start you will have more increased focus on her.

The house will be done in time for that current focus to pass to the past and be memories of what was done right and what could have been better. I would suggest that when it comes time for smallsteps to step into the driver seat, that you let your wife do the teaching, just to be on the safe side stroke wise and heart pounding palpitations. I remember drivers ed pretty well, it was a scary time.

After that your focus will shift again, more toward your wife and plans to retire for both of you and then the trips to collage to visit smallsteps, and the visits she will make to home.

most people have very little idea how much extra energy everything is taking now and my physical and mental stamina "isn't what it used to be" unfortunately.

So basically:
View it as training for the coming changes in life, because energy and mental stamina will never be what it use to be. Challenges will always be there, will always need to be conquered, and will always leave you with a lot of very nice memories. The bad memories will still be there but they will be overcome by the good ones.