Re: the spider:
https://youtu.be/PfhZB7rQ7iA?t=10The cavern levels (usually 3 of them) are large open areas that creatures can spawn in, each more dangerous than the previous. 3 options: start with at least one military dwarf and equipment, avoid the caverns until you can handle them, or know when you're close so you can immediately re-seal them (build a wall) until you're ready for them.
Iron ore (the best metal ore you find in abundance easily) is found in sedimentary layers, or igneous extrusive for hematite. Digging deeper past that only gets you trouble and magma. If you don't find iron, you may just have an embark without iron. If that happens, rely on trading for iron. Sometimes it's more cost-efficient to just buy iron equipment/toys/trap components to smelt into bars for what you need. Or steel, which is made from iron.
You also seem to be doing a lot of fishing, which is a thing you can do, but can end up with a lot of rotting fish lying around making everyone upset. If you're farming effectively, you've got more than enough food, drink, and thread (from pigtails). I think they fixed the need to get turtles for shells to keep dwarves from going insane during moods. Alternatively, fishing and herbalism can get you most of what you need if you've got an embark that allows for both, and can get off-duty soldiers used to being outside. If you want to fish, you probably want to change to zone-only fishing, and make a fishing zone in a safe section of river. Ponds run out of fish, dwarves don't know that, and you get a lot of wasted labor *and* cancellation notices that there are no fish where dwarves are fishing.
Ramps are difficult to use, and only offer a benefit over stairs if you plan to move a minecart between levels (wheelbarrows can use stairs). A 2x2 vertical staircase is usually good enough, but 3x3 doesn't take up much more space. Around the cavern levels, you might only want to go down a few levels, make a single-wide tunnel, and dig down a few more levels. Assuming you're trying to avoid having them open to the fortress. That makes it easier to seal off if things go bad.
Start brewing as soon as you start farming, and turn off your cave crops in your kitchen if you have one, and you will never run out of spawn.
I still don't know why you can't set kitchen defaults somewhere. Menu, raws, something. Having to set every single type of food/food-adjacent product to kitchen or brewery or both or neither is insane. Or at least sane defaults: seeds are neither, brewables are brewery-only, everything else is kitchen. Running out of booze because all of the emergency fruit you just gathered got cooked, or running out of plump helmet spawn because they got cooked doesn't add anything interesting to the game if it happens only because you forgot you had to make a choice, and the default was bad.