[Eridanus]

Brown algae won't hurt your kid! A lot of people deal with it, most of my tanks certainly have it.
You can always get an algae scraper (most pet stores have them) and can scrub it off that way.

The best way to get rid of ammonia is daily water changes, you can also use ammonia lock, it's by API I believe. Seachem also has something out for it.

Fin wise. Daily water changes should help that too.
Do you have a picture by chance though?

 

[Eridanus]

They're certainly necessary, and hopefully you do!

I would think that'd be ammonia, just keep up on the frequent water changes!

 

[Eridanus]

Normally you want to do daily water changes until the ammonia gets back down to 0. But we don't know parameters, so try daily changes for a few days and see if that does anything?
40-50% is good.

Your cleaning schedule is fine, is there anything in the tank that could be raising it maybe? Dead plants, uneaten food? I'm not sure if you use a vacuum/siphon or not but that'll help get stuff.

 

[Eridanus]

He'll be alright! It might stress him out at first but he'll be okay.

No need to apologize, asking is how we learn