I know how you feel. I was a publishing young-earth creationist for about 7 years in the early 80s before I realized that the geologic problems were so bad, young-earth couldn't explain them. I know most Conservative Christians don't like an old earth or evolution, but the evidence was just so overwhelming.
In my view, since Gen 1 is pre-temporal--that is, before time, the question of how long the nights are is meaningless--there was no time. My view goes back to St. Basal's observation in the 4th century that the first day is not called the first day but 'one day' and is connected to eternity past. This connection to eternity past contains the germ of the Days of Proclamation view.
So, while I might have been able to take your God is the source of light approach, the real problem then became the fossil record, the record of life doing their normal activities throughout the fossil record. The global flood failed to make a match with the data. Consider the Haymond formation of the Marathon mountains of West Texas.
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Two thirds of the Haymond is composed of a repititious alternation of fine- and very fine-grained olive brown sandstone and black shale in beds from a millimeter to 5 cm thick. The formation is estimated to have more than 15,000 sandstone beds greater than 5 mm thick." p. 87.
"Tool-mark casts (chiefly groove casts), flute casts and flute-lineation casts are common current-formed sole marks. Trace fossils in the form of sand-filled burrows are present on every sandstone sole, but nearly absent within sandstone beds." Earle F. McBride,"Stratigraphy and Sedimentology of the Haymond Formation," in Earle F. McBride, Stratigraphy, Sedimentary Structures and Origin of Flysch and Pre-Flysch Rocks, Marathon Basin, Texas (Dallas: Dallas Geological Society, 1969), p. 87-88
Several items can be deduced from thes observations.
1. It is obvious that the burrowers prefer to burrow into the shale rather the sand.
2. The burrows in the shale were present when the sand was deposited. Why? because the sand filled the hole (burrow).
3. There were few burrows in the sand as there are no fingers of shale poking down into the sand as there are sand fingers poking down into the shale.
Lets try to explain this in a one year flood. Give each shale layer 1 day for recolonization of burrowers the deposit would require 41 years to be deposited. But that is a real problem. The Haymond bed is 1300 m thick and only represents a small part of the entire geologic column. All the fossiliferous sediments in this area are 5000 m in thickness. To do the entire column in one year requires 1300/5000*365=95 days for the time over which the Haymond must be deposited. This means that 157 sand/shale couplets per day must be deposited. That means that the burrowers must repopulate the shale 157 times per day, dig holes, be buried, then survive the burial to dig again another 156 times that day. Shoot, Sissyphus only had to roll the boulder uphill once a day. What on earth did these burrowers do to deserve this young-earth fate?
We know that the burrowers who were buried did not survive. If they had, they would have had to dig up through the sand to escape their entombment. There are no burrows going up through the sand. And if there had been these burrows, there should be little circular piles of sand with a central crater pocking the entire upper surface of the sand. We don't see these. If they escaped, it should look like:
View attachment 277040
As it is, we see this, which indicates no escape of the burrowers. there is no mound at the lip of a burrow at the shale/sand interface:
shale
This is an indication of lots of time between the deposition of the sand and the digging of the burrows. It simply isn't credible to have these burrowers dig burrows at a rate required by the global flood viewpoint.
As we go east from the Marathon Mountains, these beds go deeper and deeper and are buried by Tertiary sediments which eventually reach 75,000 feet thickness in the region of the mouth of the Mississippi. If the 75,000 feet of sediment seen in the Gulf of Mexico in a one year global flood, then we have even less time for the Haymond burrowers to burrow each layer. Because the Haymond is buried by the Tertiary, we know that the Tertiary sediments of the Gulf are younger than the Haymond. Thus if the Tertiary sediment and the Haymond are flood deposits, then the Haymond may only have had less than a month for all that burrowing.
I await the young-earth explanation for this data.