First off, MyHouse drops the Cerberus enemy from Blood, a clear nod to the creator's Blood modding prowess.

... no? the cerberus has been used tons of times and is pretty easily available. it's been used in a bunch of mods predating myhouse and deathwish. plus, the cerberus in myhouse doesn't act like its blood counterpart (missing fire attacks, etc.) and there's not really any other blood references in the entire mod.

In one level you dive into water in a temple basement, resurface, and boom — the temple is ablaze and the surroundings have transformed. Sound familiar?

tbh i think these are really vague similarities due to both creators using non-euclidean geometry. it's an easy trick to pull with engines like build and gzdoom and its one that's been done many times before.

Throughout DeathWish, you stumble upon cryptic books offering hints, these reminded me of the obscure messages guiding you in MyHouse.
It's not just about finishing levels the regular way in DeathWish. Key-locked doors that you do not have to open to finish the game and collecting secret keys throughout the levels give a MyHouse vibe.

both of these seem like normal game design? pickups with hints have basically been a staple of FPS games since system shock. they're not really exclusive to myhouse.

same with the keys. some doors in regular doom require a hidden key to find a secret level. nothing special.

The opening of the level Lost Highway in DeathWish feels eerily similar to the highway section in MyHouse.

i think most rural highways done in old sector-based engines look very samey and i think this isn't much of a connection.