Removing old fireplace (Ed.)

Hi all, long-time lurker, first time poster. Have recently bought my first house and I'm hoping to get a bit of advice to help with the refurb.

One of the tasks is to expose the chimney breasts and open up the fireplaces in a couple of the rooms. Got the plaster off with hammer/bolster:


Then took dad's breaker to the bricks at the front:



Am I right in thinking that the couple of iron bars I found across the middle were simply to help protect the hole below them, and not likely to be supporting any of the wall above? Also what are the bits of wire doing there hammered into the wall? Also, someone's hacked out some of the corners of the bricks on the edge of the fireplace around where the wires are - any idea why? Do I need to repair this?

Took some more bricks out and found this:




Which looks...a bit concerning...

So finished removing the bricks in the front and stacked these to temporarily prop up what appeared to be the two unsupported columns:



I'd appreciate your thoughts on what I should do about this situation! Do you agree those brick columns need support? If so what would you recommend doing?
I guess it's a bit late now, but does that arch look OK in terms of what it's sitting on?

Finally, on the right hand side of the chimney breast someone has done this:



Any idea why there are a load of bricks missing by the wall? Is this likely to be compromising the structure of the chimney?

Lots of questions here - would appreciate any advice! Cheers!

Imagine the columns are not there and the little bit under the arch is removed too. That means you will be back to the original chimney stack. Then in the square section, that's where you install the fireplace of your choice. So depending on an open fire, or an inset or stand alone wood burner, back boiler etc.. you add material for your purpose.

So with various past installs, you have 2 columns and a little bit under the arch that catered for whatever fireplace/feature the last owner/s had in place.

Everything directly below the original arch is later in-fill and can be removed. There may or may not be a steel under the arch fixed in to either side intended to prevent any spread of the arch laterally. I suspect in your case, probably not because the sides of the breast are quite wide.