Stock subframe damage

[01somta]

I tore down my stock subframe and notice all the oops that have happened to the subframe over the past 40 yrs. I have a couple hairline cracks, which I'm not to worried about. I'll probably just grind a groove in the cracks and then have it welded up. Then only real concern is a pretty big dig/dent in the frame. I was wondering what would be the best way to fix this, what about heating it up and then hammering it back in place? Here are a couple pics of the dig/dent and a couple of the cracks (close up and far away of the cracks).

Dent

Dent

PS crack close up

PS crack far away

DS crack close up