About the close of the candle problem - https://fxdreema.com/help/working-with/on-candle-close
Drawing line is easy, also getting its price. But to detect those crosses is tricky and it depends. Here are few ways for detecting crossover and they are different: https://fxdreema.com/examples#Crossover
Lot sizing - this is controlled in the trading blocks directly, from the Money Management settings. There are various methods for this as well: https://fxdreema.com/help/working-with/money-management