SEO is not always simple math... actually, it's not simple math most of the time...
And like
@SirLouen said, KD means nothing by itself, so you can't plan your SEO strategy based on KD alone. It's the level of competition that warrants getting a certain number of links, and even that is not always the sole reason, because ranking could come down to content quality, the site's normal, or its topical authority, it could also come down to whether or not your competition buys google ads and there have been cases when google ads have outranked everyone, no matter how many links they've had... or it could also be a combination of all of these elements, and more (and most of the time that's the case anyway).
You need to learn how SEO works and when you do, you will see that there are dozens of factors that come into play when ranking certain keywords, it's not just how many links you need
direct anchor text would need
there's no exact science here, either. Personally, I like keeping the "direct anchors" (by "direct" I assume you mean "exact match" anchors, but do correct me if I'm wrong) around, or under 5%, but sometimes I go above 5% if I need to.
Currenty my position is 48th. I know I have to test but just to get an idea how much would be pbn exact anchor text backlink would be needed.
well, the best way to test would be to build 1 link (a good link I mean, not just any link), index it, and then wait (up to 1 week) to see if the position change. Unless you're in a super tough niche like forex or CBD I dare predict that 1 good link will boost your rankings by a few positions. Theoretically, it could boost your rankings all the way up to page 2... or even page 1, but - and here's where KD comes into play - a KD of 50 is too high for you to see a big boost from 1 single link (again, IF the niche is tough, in easier niches 1 link might boost your rankings by a few pages in one go, so...)
But yeah, go ahead and try with 1 link first, then another one, and another one... until you reach page 1 (or whatever your goal is)