Hello SOG
Just under one year ago I started a similar project to which you are undergoing now. I used CMC as the broker, but I imagine that IG will do the same thing. I still have both accounts, but they are not active.
Both IG and CMC have very good demo accounts. Yes, the calculations you are doing above are a very good step, and they will help understand exactly what is going on, but there is no replacement for testing them in the demo account. I say this because sometimes the multiplier can be different to that advertised. I found this mainly with the agricultural products, so my system was giving me minuscule orders until I woke up to the fact that the multiplier was different.
I found that small positions in quite a few products (between 25 and 30) gave me enough diversification to beat the CFD provider. I kept margin between 20% and 30% of account value, so was never in trouble there. Have fun with this project.
KH