Well, I contacted Gun and backerkit support and I have some answers regarding the exclusive Clothing Pack that PC physical version's owners never got and apparently never will. This is a long step-by-step post, there's a TL;DR resume near the bottom for those who don't want to read the whole thing. I also want to apologize in advance for any grammatical errors, English isn't my native tongue.
First, the guys from backerkit support. They told me that in order to access the Clothing Pack I had to install the game cd-key that was inside the dvd case, but since the game is already installed on my Steam account with the key that Gun sent to us when the physical version was delayed, it doesn't work because Steam is telling me that I'm trying to activate a product I already own. The only way I could activate that key is if I delete the game permanently from my account but doing so will also permanently delete all of the game's dlcs associated with that account. I would then need to re-buy all of those dlcs and also kiss Savini Jason and the backer's Clothing Pack goodbye since those are no longer available. And because every code is one-time use, you cannot reactivate and old code even if you try it on the same account that had that code associated with in the first place. When I told backerkit about it they still insisted that I should uninstall and remove the game from my account and then add in the new product key and they told me I should be fine. My response to that was the same as before because I know what happen to dlcs when you delete a game on Steam.
Their next follow-up was an email with a pic of all my backer's rewards attached to it. When I asked them why they were sending me this because I already have access to that list via backerkit, they told me that this was all the rewards given to me and if the reward I'm asking is not in the list, then it's not something provided to me. I then responded to them that the physical version's bonus Clothing Pack is not a backer reward in the strict sense of the term, it's something that is normally found on-disc for the PS4 and XboxOne version. But since we lucky PC physical owners only got a plastic dvd case with a code inside the only way for us to get those kind of bonuses was by sending us a code through backerkit, just like they did with the Bloody Jason Skins I received back in December of last year. Then in their next reply yesterday they asked me what level my account is at currently in-game. I don't really know why they asked me that but I gave them the answer anyway. Didn't heard anything from them since then.
As for Gun response, they started by telling me that this Clothing Pack was only retail exclusive, it would not have been sent through backerkit. Only rewards from backerkit would be delivered through that method. Any codes would be available for backers through their backer survey on backerkit.com, all codes for rewards have been delivered to their respective backers. Then they apologize for any miscommunication or confusion and said that these items are not included with the backer digital copy or physical copy. My response to that was to show them with a pic that the bonus Bloody Jason Skins I received was in fact sent through backerkit and it was not a backer reward, it's an actual bonus that is supposed to be part of the physical version. And like I mentioned to backerkit support, I pointed out to Gun that this was probably done this way so PC physical owners could have those on-disc bonuses without having an actual disc release.
I also gave them a link to a post made by Ben Strauss on the Steam forums in response to someone asking about those bonus items back in October 2017. Ben told in that thread that PC physical backers were gonna get access to them. This is the link to that thread https://steamcommunity.com/app/438740/discussions/0/1489987634016616560/ and the reply from Ben(aka ThePraetorian) is #4. Lastly, I told them that, concerning what they said about those items being retail exclusives and that they were not include with the backer physical copy, well that is simply not true. Everyone knows that the physical copies sent to backers is the same as the retail copies in term of content. In fact, those who backed for a PS4/XboxOne physical version received the exact same retail copy that is found in stores. I even included a youtube link in my email of a kickstarter PS4 unboxing video where you can clearly see the mention on the case's cover about the bonus content included. Gun's only response to that was: "Thanks for supplying what you have. I'd like to apologize for any miscommunication previously, the exclusive skins marked on the PS4 edition in the video and the ones you've been referring to are console only."
TL;DR: For backerkit it was: "It's part of the code inside the case.", then it went to "Here's your reward list, if it's not there you don't have it." to finally end up on "What's you level in-game currently?". And for Gun it started with: "Exclusives are retail only, they're not available for physical backers." and ended with "It is for all physical versions(backers and retail), but consoles only." So this is it I guess, no Clothing Pack.
I would really be lying if I was telling you that I am not a little pissed off right now. When you think about it, PC physical backers had the shaft more than once. First, like probably all physical backers of any platforms we paid more then retail price for the game. I know they can argue that they also gave us a digital copy but it was a compensation for the physical release's delay so this is debatable. Then we had the nice surprise to receive a dvd case with nothing inside but a code. Speaking of this, during the kickstarter/backerkit period I swear the I remember Gun saying that the PC version was going to get an actual disc release when they were asked about it. Otherwise, I'm pretty sure almost no physical copy would have been sold for PC knowing it was just going to be an empty case. And finally, we are the only physical backers not having access to that bonus content. Even fraudulent users on Steam have access to it because yep, that Clothing Pack is in the PC game's files. Most of the time you can see that those who hacked for Savini Jason have that Clothing Pack. I'm gonna end this post right now because if I don't, I may write something I'm going to regret.