Unless you ride quite fast all the time what you are doing is rough on the knees and not the best cardio workout. You want to spin at a minimum of about 80 crank RPM as much as possible normally. Get a bike computer with cadence to help develop your spinning ability. Unless you can output about 400 watts for an hour and well over 1000 short term you are not in TDF rider territory.

BTW high end MTB shoes such as most Sidi models are NOT inferior biking shoes but are about as stiff and effective as road shoes and are used by quite a few road riders who prefer being able to walk around reasonably comfortably when stopped.

Learning to fix a tire puncture should take less than 1/2 hour or so and could save a lot longer walk. IMO any bike rider who is not willing to learn minor maintenance is not serious about biking. You do not want to try even a 1 mile walk in road shoes and cleats. They are not designed for walking and road cleats are plastic typically and wear fairly fast when walked on much.

On exercise rides do not worry so much about aerodynamics. Poor aero just makes you work a little harder, increasing the amount of exercise you do.