Yes, the iron flesh is useful. It is the difference between the ability to make one mistake, two mistakes or three mistakes before dying.
No ironflesh + light armor = Make one mistake and you die.
ironflesh + light armor = get to make a mistake and survive!
ironflesh + medium/heavier armor = 2 or more mistakes before you die.
It is a world of difference.
As for armor, Typically light armor is best for a shielder. The shield should be your armor. Putting heavy armor on can be good for certain occasions, but shouldn't be something you think of as a regular thing. Medium armor is good too, though.
Using a bastard sword with one hand is very slow compared to a real 1h, and you have to understand that you lose 30% speed and damage (roughly) when using it with a shield. However, if you have your footwork and timing down it isn't bad! I actually have a character right now that uses 1h + shield but uses a goedandag! It is really good, so much reach + knock down! However, with that said I still recommend a real 1h weapon if you are going for battle effectiveness. They are better than half-handers.
Now, for the plate covered round shield. It has good armor -- but it has shitty HP. If you run into an axe it will survive maybe 3 hits. I do suggest a shield with higher hitpoints -- like a heavy or normal kite/norman/board shield/ huscarl* (*it is overused for a reason. Try it and you'll see.)
Now for cavalry. Cavalry is a nice variation for 1h + shield characters. You sacrifice the delicious IF for more versatility, and I like it. One thing though, no matter what I suggest getting the 100 wpf for pole arm. You'll have 130 1h already anyways!
Hope I helped.
