The EURUSD is not stable, it does not fit the economy of all the participating countries, i.e before Greece joined the Euro they had to pay double digit interests, after that they paid the same 4-5% like other strong countries. It was a nice time for the Greeks to earn money by paying lower interest, but there was a reason why they had to pay higher interests before. There is a high chance that the Euro will break within the next 5 years. If it breaks it will be over the weekend, because people cannot react quickly enough. On the day of the Brexit votum we had a 500 pip movement. This is the minimum you should be prepared if you hold EURUSD positions over the weekend. Just be prepared and use a smaller position.

WFO is good, but at the end you have just one optimal result, you don't know how the neighborhood looks like. I like this https://www.youtube.com/watch?v=B4ScXtiM3OE better. You can find Dave Waltons papers in the internet.

Moneymangement depends on the strategy. Most times I use fixed fractional, but there are strategies that always have a looser after a big winner. Then it is better to use fixed contracts. Other methods use volatiliy for positionsizing. A good book is Van Tharp - Definitive Guide to Position Sizing.