Ddlv,
we had already a similar discussion, I can not add much from what I already said. I do not understand why you make the SR rule so complicated, its easy.

1) You have a starting capital calculated from the needed capital for a TS
2) If you profit you should reinvest accordingly with SR rule.
3) If you add capital is like to start a separate TS so you do not need to reinvest using the SR rule.

Where you get the money to start trading is not relevant because you are at starting point.
You can have a margin call with your first trade if you are very unlucky. At the same time you can double your capital with the first trade using a fraction of the estimated needed capital, if you lucky.
If you survive in the market and you are profitable reinvest using the SR rule.

If you do not like my approach, use the most conservative condition you are confident with. You will be on the safe-side, maybe scarifying some profit, but in the long run it will not create much problem.

Ciao