(4) My latio also had this issue (LH side, front bumper) - the bumper clip was broken.
I also suspect it is bumper mfg defect but TCM told me somebody must have backed into my car.
If you want to fix it, get an outside workshop to replace the clip.
(FYI - I went to AS and they suggested to replace whole bumper + respray!!
I refused AS suggestion, and got the clip replaced at TCM for free since my car was still new)
(5) Ioniser is not a miracle cure. Dust/dirt/moisture will accummulate in the system over time.
Quick fix - park your car, open door/window, turn aircon to open circulation at full blast at hot temp for 15 min.
This is to dry out the moisture, and hopefully remove some dirt.
If smell persist, it is probably v dirty. Change your aircon filter, and/or send car to aircon shop to get it cleaned if needed.