1.) You say the editor runs too slow for you, but give no specificity in what is or what you are perceiving to be, “too slow.”
2.) With 4.3 - the editor will adjust various quality/rendering settings automatically based on the hardware you throw at it. You are free to turn off. You can change what it will default to under Quick Settings->Engine Scalability Settings.
3.) Someone else will have to chime in and answer.
4.) I am sure if we see Geometry 2.0 at some point in the future people such as yourself, that are stubbornly adamant about not touching any of the modelling packages available, will have more options.
5.) I would wager that you are part of the one half of one percent that thinks the new Editor is a step backward as compared to the old way of doing things.
In my opinion judging from reading your previous posts - I don’t believe you’re ever going to be happy with the new system as a whole and perhaps you’re struggling for naught. I would rather quit completely than ever go back to using the old tool-set. There are other options available to you outside of UE4, and while we all want better performance, the community is segmented based on what the community wants to see in the future pertaining to new features/enhancements.
Your wants especially in regards to going backward (in many respects) do not seem to fit in with the direction of the Engine and tools as a whole. You are still able to use UDK and you are most certainly able to pickup another package.
I am not trying to offend you, but if any product or service wasn’t viable to me in not just a single, but multitude of ways - I wouldn’t be using it - and that seems to be where you stand. If I wanted a particular model of car in black, with leather seats and a manual transmission: I might settle on the same model in white, but if the seats were cloth and it had an automatic transmission - I wouldn’t buy it! Catch my drift?