If it was me, since I'm broke, I'd make some kind of mount to hold my angle grinder and just slowly work it. An angle grinder will cut anything.

I have this cheap one and it's been wonderful. Solidly built, powerful. Best deal I've gotten in a while. I used it for almost 8 hours straight one day. No overheating nothing.

Then just buy a diamond coated cut off wheel, or 3. I use regular cut off wheels but people here say the diamond wheels are better.

But yeah dude an angle grinder will make short work of steel. It has a lock on the trigger so you don't have to constantly press it. If you're handy enough to make a contraption that could hold it and guide it you'd be all set.

If you decide to go this route be sure to watch YouTube safety videos, they can be dangerous.

One thing that works in your favor is the handle on angle grinders unscrews. That could be used to attach it to something, at least partly. Then you would just have to secure the back half somehow.