Multithreading is a huge pain in the ass to do even when you set out explicitly planning to do it. Trying to break up a single-threaded thing into multiple threads is even worse...
I've found that having smaller worlds helps, as does setting the CPU priority higher if you can. If you can possibly just dedicate a core to the program exclusively, do that. Make sure you're not running out of RAM or anything like that as well.
The stuff that worked to help FPS in prior versions for the most part are still relevant now. Don't have a billion baby animals pathing everywhere, avoid having too much junk laying around, avoid having huge liquid flows and stuff. Stockpile streamlining and setting up hauling routes can help a lot by reducing the pathing calculations. Instead of having some massive stone stockpile next to your masons that require dwarves to haul stuff across the entire fort one rock at a time, set up a stockpile near your source of stone and set up a hauling route from that source to a smaller stockpile near your mason workshops. Set the mason pile to take from the source pile exclusively. A bucket-brigade sort of hauling system works well (shorter distances = shorter pathing calculations), but setting up a track and minecart is great particularly for when you are moving stuff very long ways. Intermediate stockpiles and hand-hauling is just fine for things like wood hauling from the surface, usually.
Setting up a minecart and track system means you can have just one dwarf guiding a cart across your fort and back for every load of N stones, instead of having N dwarves hauling N stones by walking back and forth and back and forth... you don't NEED to have the tracks powered with rollers, a dwarf can guide a cart uphill just fine. If you want to automate it by all means feel free to do so, but it isn't explicitly necessary.
Turning off temperature and weather has a HUGE effect on FPS for me, but that's at the expense of not having temperature and weather. I'll drop a good 40 FPS when it starts raining in my fort. It's up to you to decide if you want those things or not. Personally, I really like having the weather and temperature so I just grin and bear the framerate hit. To each their own. You can change the settings without needing to regenerate the world (you will need to save, exit, and reload, though) so see if it helps for you.