Definitely wear the leather armor for now. Leather armor +2 is better than chain mail +0. I would try to identify the plates. If they are +2 dump upgrade scrolls into them so that you can wear them with 15 strength and then do so when you reach that. Or try to reach the smith and upgrade the armor with his quest reward.

What wand did you get from the wandmaker? My usual approach is to imbue my staff with that and then use it as my main weapon and upgrade it further.

A good idea would be to infuse your staff with your wand of corruption and then upgrade it

You probably just want to get heal pots from f11 shop, out your 4 sou into that sword and armor to get them both to +3, so you can wear them both with 15 str. To survive until you get bot pos from f11-14, put 2 or 3 sou into your evasion ring to boost your ehp. With t5 weapon and armor and chains caves boss should be a breeze, and you can snowball the run to ascend