You asked how realistic the strategies are:
What robustness tests have you performed? How many bars? What timeframe are you using?
As to widening spread killing the strategy two suggestions if you are concerned about this then here are a few suggestions to check this out:
1. You can simply increase the spread from 10-20 for example and see how it affects your strategy
2. Run a monte carlo on spread only
These shouldn’t show much effect as generally the strategy will simply improve if you lower the fixed spread and and vice versa if you increase it.
A check I often perform is to change the trading session time in tools from 00:00 – 24:00 to 01:00 -24:00 as I have noticed that this can be quite a volatile time for spread and so it has a measurable negative impact I personally don’t take that as a good sign.
Of course the most accurate way will be to run it on a demo and see the results when trading real-time with variable spreads.
If your strategy passes all those check then I wouldn’t be concerned about spread (In my opinion anyway), but there are many more checks required to increase the probability of your strategy being a robust one. Its as much an art as a science I reckon.
It can be quite easy to get excellent results as you have shown but you have to be careful that you have not simply allowed EA studio to curve fit results.