The failure to add pit traps due to it being marshy is not a great setback: just use bear traps instead. I haven't seen any difference in how they operate from a practical point of view anyway.
When it comes to burning for fields, I make mine 9*9 (you can harvest 3 lines by walking along the middle one, so that makes three sweeps at harvest time), and I place branches on every tile in every second tile (usually prepared during winter, at which times the trees are removed as well). I then set fire to all branch piles in a line, and by the time the last one is lit the first one has usually expired, so I go back and prepare the soil. I then do the same for the second line of branches (on the third line), and by that time it's usually time to call it a day. Once all the lines have been taken care of, I place branches on the unprepared lines and repeat the process. By not burning more than I can process in a day (or the next one, if I'm unlucky with the RNG so preparation takes unusually long), I make sure I don't waste burned tiles due to interruptions such as having caught an elk in a trap (which takes about two days to take care of).