1/8″ bit has a much lower load on the gantry. You should get better results compared to a 1/4 bit.
Trichoidal might be a waste of time on wood. Probably faster just to make a few more shallower passes. A really deep pass put a high load on the bit because it is trying to push the chips/waste out at the same time it causes it to get cut again. So you end up re-cutting chips. I just did a 1″ deep walnut block and used a 1/8″ at 3-4mm per pass 15mm/s no issues with a 2.5″ zaxis.
Your z axis is also hanging really far out. You will gain a ton of rigidity moving the block up on some spacers or shortening the legs on the machine.