Lot size calculator improving

I need to improve the attached code in order to be sure it works in the due manner.

I wrote the code to calculate the lot size before to open a new position.

The code must works for forex, CFD and CFD-leverage.

The code must also works with brokers where the margin rate is not available, as follow 

SymbolInfoInteger(Symbol(),SYMBOL_MARGIN_INITIAL)=0

First step is to calculate lot size from a certain max % of free margin. I need the required margin for the new trade to be less then x% of available free margin.

Second step is to calculate lot size from a given % risk.

If lot size from % risk > max size from first step, then rescale the lot size to this one. 

Thank you