Hi welcome, my opinions below
1) I feel no need to replace, as you already have compartments of ceramic rings which essentially serve the same purpose as chips. Ceramic rings might be more porous too, making them more beneficial to house bacteria.
If the wool is in the earlier compartment before your rings, they also play an important role in reducing detritus from reaching your rings. This minimIzes chance of nitrate accumulation.
2) flow is relatively ok, abit low maybe if you intend to keep SPS. But you can always add wave makers which are more effective in providing good water flow.
3) air pumps as a precautionary measure are placed higher, so that if pump stops for whatever reason, water doesn't get 'siphoned' into the pump