Yes you must breed with ditto. Same thing like magnemite is breeding with Ditto cant get IVs. Same thing goes for Phione and other Pokemon.
Source I IV breeded a lot of magnemites
Yes, if you have a high IV Ditto, as genderless Pokemon can only breed with Ditto.
Source: Doing it right now with Rotom :P
Yes you can, but you must breed with a Ditto.
Source: I've done that several times.
Hope I helped