Coax length for EFT-10/20/40?

Hello!
I wanted to ask three questions:

1) Is there a recommended length of RG-8X coax I should be using with the EFT-10/20/40. I have a 50′ RG-8X coax cable. Can I use this?

2) Is it advisable to wrap the antenna end of the coax through a ferrite toroid or is this not necessary? I will be putting out a maximum of 20W.

3) I am planning to hang the antenna vertically off my 17th floor balcony with some sort of weight (maybe a fishing line weight) at the end to keep it from flapping around. I will tune the antenna in that position. But if I take it with me to some other location and mount it as a sloper to, say, a tree I would assume the SWR will change. I am worried that I would need to add wire back at the end in that case. Do you have any advice for such a situation or is it unlikely to be a problem? I do have an MFJ-9201 QRP tuner to help.

Thank you!

Nico