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I’m trying to hang 2 shelves on my wall and am hoping to put some plants on them so they will have to hold a good amount of weight. For reference I’m trying to install these shelves: https://www.amazon.com/gp/product/B07GQN322Z/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

I’m running into some problems and was hoping someone could help me.

1. Using my stud finder I found 1 stud in the area I wish to hang. Assuming I can get one of the supports on the stud and use some kind of wall anchor on the other how do I estimate how much weight it can hold?
2. For the stud, I’ve tried ~4 different locations (see image) and I keep hitting something. At first I thought it was a nail so I moved to another location. Then I hit it again and thought it was less likely it was another nail. The third and fourth tries were just me trying to figure out what was going on (spoiler: I didn’t). How can I tell what I’m hitting? Or am I doing something fundamentally wrong?
3. If q2 leads to some answer that removes the stud as an option and I have to use wall anchors for both supports how do I estimate how much weight it can hold? Any wall anchor recommendations? I feel like it would depend on what kind of wall this is but I don’t know how to tell, I think it is drywall.

I would appreciate any help/tips/advice/references!

https://preview.redd.it/hki6czpinhx31.jpg?width=3024&format=pjpg&auto=webp&s=5ae59f79d8ae8aced66dba54f7498354b4f86c07