I'd recommend buying 70 attack strength defence, range, attack mage before trying barrows. There is no need for that, only 70 ranged mage for OSRS Gold the MSB or mithril bolts that Zanik's C'bow has. It works for me. However, I've seen better results today.

Optional: get DT completed for Ice burst, unless of course you already have 55 slayers. In that case I imagine you can use magic dart. If you decide to do this, you'll require a canifis portal inside your house, which will require the completion of DT (or it will take longer to get there or whatever). It's not required to do DT, but it's a fun quest and you'll want to finish it sometime in the future so having it completed now would be helpful. While you do not need, 70 att,def,str,range and mage would help greatly. Magic dart can be a useful alternative...

Absolutely not, but I'm talking about the melee levels? You really, really aren't required. Barrows runs work without them. I'm sure that 70 defense might be helpful when you're using ice magics, you never need to melee anyway. Not at all. Karil gets lost in magic and ahrim is slower to travel.

Admittedly I don't normally do more than 1 run each time, but this is because I'm not able to get to the end of my maze. (This wasn't until I got some of the levels you've mentioned). I'm sure I could do two or three sessions at a time.

70 defence is very very beneficial when using Blitz to Sally and is among the most effective methods(if you aren't able to access to turm/chaotics). Attack and strength speed up Ahrim, however it isn't necessary and 70 mage is an absolute minimum. 82 is better.

The following is my current setup: Sacred Clay Helm Granite body, Dragon Platelegs, Amulet of Glory the ring of wealth, Obsidian cape, Dragon longsword, obsidian sheild/Mithril defender. I am in the process of buying 1 mil of gold to upgrade my armour/ wep. Notice: I'm in need of exp so i wont change the helmet. I haven't done the freminik quests either. I'm planning to Buy RuneScape Gold switch the black boots to dragons after I've gotten a few more 100ks. Haven't done monkey madness. I'm working to obtain dragon defender btw...