Purely subjective.
When do you feel comfortable throwing all of your cash at it? You are going to get a lot of different answers. I will throw mine in as well:
- What is your maximum exposure?
- What is your risk-adjusted metric? (Sharpe, Calmar, etc)
- What risk-adjusted metric number makes you feel comfortable? (Ex. Sharpe > 0.8)
- What is your maximum drawdown, and why? Where do you lose the most?
- Can you explain mathematically why you win when you win?
- Have you walk-forward tested your system? How does your system do when trained for N days and traded for N+X days?
- What is your risk of ruin?
- Based on (7) what is your ideal capitalization?
- Have you looked into the kelly criterion and determined your maximum leverage?
These are just a few things I use to evaluate a system. There are many more - for example 50 trades is a statistically significant sample for an approximately normally distributed variable (i.e. log returns) but wouldn't make me feel comfortable in terms of total performance. Fat tails make me more cautious which is why I look to ruin analysis.
I will unfortunately break the news to you that I think everyone else is ignoring. If you cannot program a strategy you are doomed to failure. You are removing the ability to walk-forward and monte-carlo test your system. You are removing all ability to do any sort of real analysis on your system performance over time. Since you cannot program the system pay someone who can. It could be as simple as an excel sheet or an R script. Pay them out of your investment capital. This investment will save you many, many thousands in the long run.
Hope this helps. There is no easy answer. You are going to get a lot of garbage responses. Especially in a forex forum. If you cannot mathematically explain your edge you have no edge. End of story.
EDIT: Sidenote: You can tell a post is worth ignoring based on the amount bold in it.
I cannot answer any of your questions

But i will look all of those things up and get back to you.
I only just discovered backtesting, and i landed on profitspi for this. I understood intuitively that the last two years (as far back as my current subscription allows) is not a reliable indication of success. I'm going to go ahead and pat myself on the back for that, and yes I am absolutely seeking everyone's approval. I also figured on a way to "walk-forward" test it, but i didn't know that was what it was called. I will look into monte-carlo testing now.
to answer your questions, for now:
1. i don't know what this means yet
2 and 3. just looked this up, i will get back to you on it.
4. -25.5%, yes i know why and i find it acceptable.
5. yes, but in the way Dr. Malcolm explains chaos theory in Jurassic park...does that count? Or do you seriously want me to come up with a formula? Becaue that exceeds my capacity and laziness threshold, and i don't believe it would be worth the effort. Feel free to correct me if i'm wrong.
6. I'm halfway through figuring this out. I developed my strategy using three start days based on what i considered the worst time to get into the market (at a peak right before a drop), the best time (the bottom of that trough) and a neutral day (as far back as my backtester could go).
7. I'm glad i looked this up, and i will run the numbers to confirm this, but i want to say 0%. thank you for making me aware of it.
8. I want to see a 50% annual return if that is what you mean. I'm happy with a 5% outperformance of the s&p500.
9. nope, but i will put it on my todo list.
I have some questions now. Once i fully test the strategy out and iron out more of the wrinkles in it, how do i even implement it? I use TDameritrade, and just opened up thinkorswim today to try out the papermoney trading feature. Bottom line is, I won't be using TOS. I plan on doing the paper trading with excel now, but any suggestion is welcomed. I will look through the sponsors of this site, and a forum search in the meantime.