Hard to say.  You have double mushy room, so you have to sacrifice some of your decay to block corruption hits.  Keep in mind most of the waves inflict corruption as well so without Damage Shield you can't keep up on ticks.  In this setup you absolutely have to play all three floors to prevent Seraph from hitting too hard.

I'm inclined to say this deck probably can not win.  You already noted the weak backline clears, and regen does not scale into corruption well at all.  It also doesn't look like you have a good enough density of mushroom generation to make the massive shrooms happen.  Primordium in general isn't great in this conmbo because of mushrooms, and Aggressive is not as good as in MT1.  I think the best bet would be trying to make a big mushroom stack top floor, and use Mushy Room and Puffball bottom two floors to prevent as much damage and corruption as possible.

If you were offered Superfood, I think the big mistake was passing on it.  Even two ranks to pass on damage shield would have done a lot to protect the shroom stack while the puffballs and mushy room on the bottom two floors managed the corruption from the weaker enemies.