2007 R56 N12

I understand this is a frequently discussed topic, so bear with me.

Car has a rear main seal leak and ongoing cold start problems in extreme cold (-20c or colder). I was recently at the dealer for an unrelated recall and was discussing oil weights with the advisor. He said a rear main leak is very rare and suggested both issues may be related to the fact that I'm using 5w30.

Supposedly, 5 weight oil may be too thick, causing PCV issues which may be putting excessive pressure on seals. As per the manual, 5 weight is the correct oil. I normally change my own oil, but in the past a trusted shop also used 5w30. He told me I should only be using 0 weight oils, BMW does not recommend 5 weight oils, and that I should not go to a shop that uses 5 weight. So I'm kind of confused. Should I be switching to 0w30?

I should mention this car burns significant amounts of oil during the summer when it runs at higher temps for longer periods. About 1L every 700-800km. And this was before developing its most recent leak, so I'm confident this oil was being burned not leaking. During the winter, it burns minimal oil. Last time I checked the PCV valve I didn't see any obvious signs that it needed replacing. So I'm reluctant to switch to a "thinner" oil that may increase oil consumption.

I attached screenshots from the manual of a 2007 and a 2009. Why do they have different recommended weights if they have virtually the same engine? Any recommendations for what oil I should be using given this information?