The clean air intake and PCV to the manifold should be separated by the entire engine if possible to pass all the crankcase vapor through them. If they're both on one cover the case is never "flushed" and accumulates sulfuric acid and combustion products.
Severe blowby is generally ring seal going away, and you already know what fixes that.
A much bigger pan volume (longer, deeper, wider), for more air not more oil, reduces the amplitude of pressure spikes, so will any extension to the valley or covers. It's only a buffer, so shape doesn't matter as long as the connection to the air under the crank is large.