Can’t offer much help in the ways of 1 and 2 but as far as 3 Amazon should ship to you? I ended up picking up a compression spring assortment kit of various sizes to mess around with I’ll edit a link shortly

Edit: Compression Springs NEWST Spring Assortment Kit | Stainless Steel Springs | 17 Different Sizes 148 Piece Spring Assortment with Case https://www.amazon.com/dp/B08RXV6WH2/ref=cm_sw_r_cp_api_glt_i_V7GN94YR0XQHN05AEAHP

Aside from that do a little research on google, there are a couple sites that offer aftermarket springs but those will prolly be way overkill for what you’re doing