It would be a bit better if you could knock that gray paint off if that's what it is, but for the otherside, that is plenty good enough. Probably much more than necessary and should work very well. You see all that pitting? That is the damage rust does to iron. Rust will eat steel and iron, and that stick there is proof positive. But, still good for this process. It'll be an awful wide cut, but you can probably cut that steel in half with your angle grinder blade if that is all you have to cut it. I happened to have a chop saw and what I used to cut that 1/4in strap I had.
Oh wait, you have a sawzall right?? I assume that is what you called a saw saw, better know as a sawsall, as in saws all. Put a metal cutting blade in it and cut it with that.