Humidifiers and Dehumidifiers - Humidifier T'd off washer supply line?

Hello everyone,
I've been reading this great forum for a while now and finally decided to type in my first post. I'm getting ready to install my new Desert Spring humidifier (hopefully this upcoming weekend) and I hope you don't mind I post couple questions here. I have an old (non-working) humidifier installed on my furnace and a saddle valve pierced into a pipe near the basement ceiling. This valve is not attached to any hose and I'm planning to just leave it that way (there's no leakage of any kind). When installing the new humidifier I'd prefer not to use another saddle valve but rather have a 1/4" copper pipe connected. In a distance of couple feet from the new humidifier installation place I have a hot and cold water pipes that supply water to the washer. My question #1 is as follows - is there any reason for NOT splitting the washer cold water supply (there's a threaded end there with a ball valve) and connect back the washer hose to one end of the T and another ball valve (so I can shut off the water supply to the humidifier) with a compression fitting for a 1/4" copper pipe that'd go to the humidifier? If this could be done, then I wouldn't have to do any pipe cutting or soldering on any new fittings... I don't believe there should be any problem but thought I'd consult professionals first since I don't have basically any experience when it comes to plumbing (except for some threaded fittings). Question #2 - is there a limit to 1/4" flex. copper pipe length? Would approximately 6' of pipe be too long to run to the humidifier (I'd support it if neccessary)? Question #3 - I don't think there'd be a problem if the T'd off ball valve for the humidifier is about a foot lower than the end of the pipe (i.e. where it enters the humidifier)? And one more (Question #4) - how should I connect the copper flexible pipe to the humidifier? The fitting on that end is made of plastic since it's designed for the flexible PVC hose that comes with the humidifier)? I realize these are quite a few questions for a first post, but I'd really greatly appreciate any feedback. Thank you in advance.

1-I'd put a T in the up away from the washer hook up. When you are not washing you have that valve shut off, (If you don't you should)

2- No, there is no limit on the lenght of run. Just support it so it not bouce all over when the valve inside the humidifer open and close.

3- no problem if the valve is lower or higher than the humidifer itself, the water is under pressure.

4-As long you use the brass nut, and brass ring, you should be fine making the connection.

Like said . But use the hot water line there. Come up off that T to a 1/2"mpt. Then get a shut off like for a toilet.
1/2"fpt to a 1/4"compression fitting. We use that 1/4" plastic line all the time .

Thank you very much for your input guys. I'm going ahead with the installation tommorow. I'm just still not sure whether I should go with the copper pipe or just the plastic tube. I estimated I'd need about 11' of pipe to reach my humidifier...