In theory and in paper it all looks good thus far. But as you probably suspected E-2 applications are not that simple or predictable and the particular US consulate overseas where applied can also make a huge difference, since US consulates are very "country sensitive". In addition, both your applications will be made more complicated by the fact that each of you will be investing 50% - 50%, arguably "diluting" the value of each other's investments and also possibly "canibalizing" the...
The answer to your first question is a definite "no".
As you are not now in H-1B status, you are subject to the numerical cap.
Consequently your employer can only file a new petition on your behalf on April 1, with an October 1 start date.
No! Don't worry. No new law or legislation passed by Congress can go into effect retroactively. That would be unconstitutional. As long as one files a siblings' petition prior to the F4 category being eliminated, that petition will be accepted and processed.
By "eliminating the backlog" what is meant is that the pending cases which were filed prior to the date of elimination of the F4 category will be processed faster and more efficiently, until there will be none left.
Before you listen to any other nonsense, do yourself the favor of downloading the instructions to Form I-130, from the USCIS website www.uscis.gov I think those simple to read instructions best describe the monetary and criminal penalties for those U.S. citizens who engage in marriage fraud, then decide for yourself if it's worth it.