There's plenty ( plenty) of steel weapons, i made like 600 steel bars and turned that into 20 sets of full squad armor along with steel axes. And i have another iron set for backup.
I'm on a very weak rig so i played with a pop cap of 80 and i dont like pump stacks for the fact that they consume masses of resources ( especially with the new version ) and are a pain in the ass to set up.
The top layout was actually well thought through, because the gobos would have to enter the fortress over a long narrow bridge to get to my barracks via stairs.. the problem was that my dwarves ran out of my fort chasing elk bird riders thus leaving the fort open to those stray trolls....
the elk bird riders were like a lot faster and my dwarves just kept chasing them whilst the marksgobos took them down, it was a very sad battle.
Actually pump stacks don't have to consume huge amounts of resources (fps or material) there a few designs that have nearly no impact in fact. Plus it doesn't have to be always on, just when you need it. Materials for them aren't that bad especially at this point in your fort or earlier if you hadn't gotten taken out back and violated by all the trolls.
I tend to play on 200 dwarf pop caps so I account for 300 with children (may have to increase that with the current migrant waves) so my forts tend to show that. For 80 I can see the design being more feasible if still a bit awkward feeling at least to me.
I have to say while I understand what your idea was on the top layout, I just don't see it working mostly because dwarves aren't recruited for their brains. Traps would be my next step, set up a parameter with dogs/cats/something then traps around the fort then a way to seal the base proper while leaving soldiers a route to the battlefield to protect the workers. That way at worst your army gets destroyed but your infrastructure remains undaunted. Least from surface attack. From caverns and HFS requires a different approach.
Additionally you may want to think about wider hallways. There's a lot of traffic congestion potential around the stockpiles in the facility. Also squaring the staircases up and down also tends to be bit more efficient than a line of staircases as far as dwarves getting to where they're going.
Good luck Splint. If you can get a decent migrant wave and not get attacked for little bit you should recover pretty well. Resources are there which is normally the deciding factor. Long as you have food and drink you should be able to recover and get back on track.