Farming Questions

[Jasper#5503]

Hi there, I was wanting to create a spreadsheet for what's the best way to farm gold from crops and had a few questions over how the game calculates certain things, since the wiki didn't clarify these things.
1. The 'Thrift Hunter' skill. When it does the 5/10/15% off for seeds, will it always round up or down if it can't get an exact answer, or is it just the closest whole number?
2. For the 'Propagation' and 'Fertile Land' skills, do they stack, or are they exclusive? If I had +4% from Propagation and +4% from Fertile land, would I get a +8% chance of an extra crop on fertile land? Or does Propagation only work with unfertilized land?
3. Similarly, for the fertilizers, the wiki stated that fire fertilizer 1 and magic fertilizer 2 have a 30% increased growth speed, while tier 2 had 50% increased growth speed. Are those just calculated by growth speed *.7 and *.5 each? And again, rounded up, down, or just nearest whole number?
4. does the earth/magic fertilizers stack with both Propagation and Fertile land?