10cm can make a difference but, as you said the water is clear, it should be fine. Perhaps even better.
Not sure about the gloves, I wear neoprene as the water here in the UK as it is cold. Kevlar is stiff and used in bulletproof jackets. I believe Dyneema is similar but it is less stiff; not sure if is used for bulletproof vests. Both have been used for climbing protection but Dyneema/Spectra seems to have taken over because they behave more like rope. Both are hard to cut, perhaps Kevlar more so?
For beginner spearing fins I would recommend something with plastic blades. I prefer replaceable blades but it is not essential, plastic blades can last 10 or 20 years, perhaps more. I use and like Beuchat Competition fins - I have 2 pairs and a spare blade and fitting kit - good footpockets for my stubby feet yet also rated highly for slim feet. The Omer footpockets are highly rated too. Again, one of the cheaper plastic blades models would be my suggestion . Omer and Beuchat footpockets are popular so if you want to "upgrade" to more expensive fibreglass (a popular option for spearing) or lightweight carbon fibre later, you have that option, if you choose a model with replaceable blades. However plastic blades work perfectly well for my spearing needs.