If you have to ask which language is faster (C++, Python) I strongly suggest you stay with your Jigsaw (DOM) trading and do not embark on this project.
In TV show terms, Trump has "jumped the shark". Sure, the hardcore fans will keep tuning in, but most are moving on to other programs, though we may drop back in for an occasional re-run :)
I ran into road blocks with MultiCharts that I was able to solve with QuantTerminal (mainly running a portfolio of strategies with multiple time frames per strategy). Might be worth checking out.
I am not familiar with TOS, but try placing the virtual trade and the previous days close. That might result in a fill at the open as that is how most backtesters operate.