@MH74, these margin requirements are for naked/uncovered puts and calls. None of SO trades do naked puts/calls. So your margin will be dictated by the distance between your long and short legs. Since standard official SO trade size is 1K, your margin should never exceed 1K (of course multiplied by how many units you are trading). Hope it helped.
In the past six months, I have traded SO calendar setups in a Tradier account when the account balance has been just below $2K USD. It may have even gotten down as low as $500 USD at one point.
To keep it simple, the RV decline is deducted from the return of the ratio to ensure that the return is not overstated. Some stocks have higher RV declines than others and hence the deduction is generally very relevant.