I'm not sure where we are disagreeing in regards to the toledot
The thing is when we see the towlĕdah phrase used (i.e., "these are the generations of..."), such points not to anything prior, but what is about to come after. This is the way it is always used in Scripture. Therefore, its use in Genesis 2:4 isn't saying this is what happened after God created the heavens and the earth (which would be to point backward), rather it is like the start of a new chapter.
I think I agree with what you are saying above...
Genesis 2:4 is continuing forward from where Genesis 2:3 left off.
The phrase "when God created the heavens and the earth" describes the point at which the narrative beginning with Genesis 2:4 is proceeding from.
"when God created the heavens and the earth" describes what occurred in Genesis 1:1-2:3.
Therefore, the toledot tells us that narrative beginning with Genesis 2:4 proceeds forward from God creating the heavens and the earth (Genesis 1:1-2:3).
To be honest, since I embraced Genesis 2:4 as the introduction to the second creation account (based upon the logic that the toledoth phrase, "These are the generations of
", only ever points forward), I'd not considered a "from" point as you correctly emphasise is given in Gen 2:4b: "in the day that the LORD God made the earth and the heavens.
I think it's important here to note the order of "heavens" and "earth" which isn't "the heavens and the earth" as you accidentally paraphrased, but rather "the earth and the heavens". I've actually been writing a more full post, in my typical long form, to elaborate upon what such means mixed in with some other thoughts.
Nonetheless, I do essentially agree with your observation above. Where I differ is likely where the "from point" is i.e., what "the day" specifically refers to. However, as an argument against YECs claiming days are 24 hours, I do believe the second half of Genesis 2:4 forms a strong argument against interpreting days in Genesis 1 as a period of time.
So then, Gen 2:4b further supports (in addition to the Hebraic poetic form, parallelism and strangeness of days existing without a Sun that isn't made until Day 4) that language or ordinary days in Genesis 1 are being used to provide a literary framework wherein creation events are described.