Zoom APF-1 Accessory Pack for F1 Field Recorder

If you're referring to the 3.5mm jack... Assuming your Sennheiser mic also has that jack size, then yes, there won't be any obstruction or interference stopping you from using a higher-end mic of your choice.

Yes, using https://www.bhphotovideo.com/c/product/1358231-REG/rode_vxlr_mini_jack_to_xlr_adaptor.html?sts=pi&pim=Y

I believe it can be used with the H6 via the 1/8 jack on either of the XY capsules that are compatible with the H5/H6 (download an H6 manual and check out around page 88). Of course this requires the capsule to be installedmight affect your size/space constraints. The other concern is whether the locking ring will interfere with plugging the mic into certain devices with a tightly-packed I/O design, and you wont be able to screw down the locking ring since the jacks on the H1/H2/H4/H5/H6 (accessories) do not have male threaded locking rings. Good Luck.

The cable for the LMF-2 Lavalier Microphone is 63 inches.