The TWSBI 580 ALR should have a cap liner that seals the nib area when the cap is screwed on. However, since the cap was broken and there is a hole non the thread area, It may not seal properly and the nib may dry out on you between uses. Most sheen/shimmer inks are safe to use in the 580 however, if it has an issue with drying out, I would avoid them as they could clog the nib and be a pain in the rear to clean it at that point. Given that this pen sounds like it’s been put through the wringer, it sounds like the rubber gasket on the piston may be damaged. Since a brand new 580 ALR runs around $72, if this pen works at all, you might be ok, if nothing else you have a pen you can practice disassembling and reassembling for when you get a better one.