FWIW, I stopped kegging my saisons and other belgians entirely. I've tried +6mo ones old bottled naturally and bottled from keg (CO2 purged w/ beer gun) and the naturally carbed ones hold up much longer IME. Hell, I have a few that are 18 months old and still held up better than the ones I bottled from the keg. That being said, if you just want to drink it all on tap, go for it. I bottle them because I like to give stuff out and be able to transport easily
I haven't had issue with priming calcs. I had some batches overcarbed early on, but I attribute that to not dialing in my volume being bottled. The rule of thumb I use now is the wort level minus 0.5gal due to trub loss. But I always take a look at how much trub there is and try to guess from there at the final amount that makes it into my bottling bucket.
For saisons, I usually aim for 2.8 vol co2. You can go higher, but I've read rules of thumb that you dont want to exceed 3.0 in most 12oz longnecks/shortnecks. I figure at +3.0, any small defect in the bottle may cause issues
The one thing I dont entirely understand is the temperature calculation you input. I always just use 68-70F, as that is the room temp its sitting at when I bottle. But I read everywhere that you are supposed to use the HIGHEST temp it ever achieved during fermentation. For me, thats about 92F. But when I tried this, I got very overcarbed bottles. Plus, the other stuff i've fermented at room temps and primed to the same 2.8 turn out very similar to the 92F saisons. I dunno, maybe it has something to do with the 3-4 days they sit at room temp before bottling. Maybe this equalizes the already dissolved CO2 levels.