the welds will distort the angle. if you must use angle, get some that is thick enough to tap your threads directly into.
the only thing that iron lends to the jig is a level of stiffness that is difficult to achieve without a large amount of wood. you certainly don't need that much stiffness for this straightening/tapering jig, and the weight and certain disaster should the iron contact the teeth of your blade are enough to rule it out in my shop.
for kicks, try to do this entirely out of wood- no nails or screws even, just glue. make the toggle. be inventive. this is the kind of jig that you should be making as the need for it comes up, out of scraps that you have on hand. you get extra points if it works the way you were imagining it the first time you make it, and you get points off if you spend any money making it.
think about it: the basis of this jig is a straight reference edge a bit longer than the board you want to work on, wide enough to support the workpiece and stay straight while feeding it through the saw, thick enough to take the forces of clamping your workpiece to it......