Your post is pretty light on detail - normally with a case study people try to share how they did things rather than just dumping stats and a little "about me".

You said you have a background in SEO and link building so you might already know this, but you have to be careful with the links you build on a brand new site, normally people want to build a small amount of super high quality links in the beginning months until you start seeing enough traffic/rankings for a lot of links to start looking natural.

Going from DR6 -> 17 -> 33 is a big jump early on, and while obviously DR isn't a ranking factor it does suggest a lot of links were built, and that could be a red flag to google as why would a brand new site get that many links so early? If it's a new subsite of an existing brand it would make sense, like Nike launching a new product line or similar, but if it's just a random affiliate site with no real brand presence, it's going to set off alarms. I personally know multiple people who have tanked new sites this way.

Again, you said you have a background in SEO so you might know this, but you also say you have 5 sites you use for selling guest posts so you might just be assuming any link is good.

Either way, good luck with the site. Maybe ramp up the content a bit - lots of short posts for super low volume keywords will probably give you a bit of a topical boost early on, it's how I like to seed new sites.