Hello Zalus, and let me introduce to you what I believe could be exactly what you’re looking for! 
I run a server that has everything you mentioned:
~ it is roleplayed (RP is enforced, you’re not allowed to break character in chat)
~ it is slow and immersive leveling (XP rate for the kills is x2, however the rest XP is decreased, and also it is hard to get the kills, see below)
~ the settings are hardcore and focused on making the survival challenging and rewarding (in short, you are twice weaker while the mobs are twice stronger)
~ the mobs and the resources respawn 3 times slower, so you are forced to fight for the resources (fight with other players in fair PVP)
~ the buildings are way stronger and hard to explode, while the explosives are way harder to obtain (yet it’s still possible of one is really determined)
~ dynamic building damage to protect your belongings while you’re offline (30 minutes after you log off, to prevent abusing)
~ no limitations in terms of roleplay, pvp and building (except for the obvious cheating, griefing and abusing)
~ there is no global chat, so nobody will interrupt your immersion while you’re exploring the world
~ everything above is being achieved through server settings, there is currently no mods
Yeah and did I mention, all that is for free? 
Just hop in and give it a try. The server is new, so there is no crowd to disturb you. Yet! 
Here is the link to forum topic: Full-RP PVP Survival [EU Server]
And here is the direct IP to join the server: 46.4.244.169:17000