Here is what I found. It appears that the heat of passion defense could reduce a second degree murder from a class 2, to a class 3 felony, which are generally punishable by 4-12 years. However, since it is a violent crime it pushes it to up to 24 years.
So if he wins on heat of passion defense for the murder of SW and is not convicted for the murders of his daughters, he is looking at 4-24 years for murdering SW, from what I can tell:
"Second degree murder is a Class 2 felony generally
penalized by a presumptive minimum of 8 years and maximum of 24 years, with five years parole. However, second degree murder is a violent crime which has a higher maximum of twice the usual maximum sentence, thus 48 years would be the presumed highest end of the punishment range.
Murder in the second degree is reduced to a Class 3 felony where the death was caused during a sudden heat of passion, caused by a highly provoking act of the victim, which excites the defendant sufficiently, and that a reasonable person in his or her place would also be provoked. However, if there was time to cool down from the excitement, it would be a Class 2 felony.
Class 3 felonies are punished by 4-12 years, but again, as a violent crime, 24 years would be the presumed upper limit."
Colorado Second-Degree Murder