Retarding?

so I’m finally getting the hang of a particular sourdough recipe, but I’m still struggling a bit I think with retarding.

my basic recipe I’m working with works well when I do the first and second rise at 25ish Celsius for 3 hrs and another 2 1/2 or 3hrs with all the folds and everything in between. Though I do still feel like I’m winging it most of the time 😂. But it works good.

now my fridge can be anything between 0 and 5 Celsius sometimes a bit higher if I’m in and out of it. 
hopefully my question will make sense- at these cold temperatures, how long do I proof it to get the same  result as if I had proofed at 25 Celsius throughout the process?

is there a calculation of sorts? As I’d be curious to work out how far it could go, say for example at 1 Celsius it would take however long, at 2 Celsius it’ll take however long, and so on and on. Does such a tally or calculation exist as I can’t seem to find one? Or if not, how do I work it out?

I think I understand that at colder temperatures the poke test doesn’t necessarily work as the dough would be tighter and otherwise act a bit different and also not rise as much if at all, but just a rough timescale would be good, that way iv a benchmark of when it should be ready. And is there a point when it’s too cold for the dough to do anything?

if it helps, iv done the first rise at 25c for 3hrs, iv then put the dough in the fridge at 4 o'clock, then baked the following morning at different times to see if the results differ, one at 6 o’clock, one at 7 o’clock and so on till 10 o’clock and once at 12 o’clock  (on different days. Not all one after the other). Do it had anything between 14 and 20hrs.

the results are generally the same, a bit dense; heavy and a bit tight. Doing it at the warmer temp (once I’d got it right) gives lighter bread, once I purposefully let it rise for another 2hrs to see at what point it would over proof, but they came out even lighter, like a burger roll/bap, so I know I can get soft and light loaf this way, but have not yet cracked the cold temp rise. 

Iv also done 2 warm rises for a total of 6hrs and done a cold retard for 14hrs but this loaf collapsed; possibly a result of my starter being less active than it is now, but I reckon at this point it was overproofed anyway.

Any advice/tips/pointers, as always is very much appreciated.