Hello,
1 - The vendor fees are based on what the client has paid.
It cannot be relative to the "retail price" since it's just a fixed number without currency, or else.
What you're asking is not possible since there is no possible relation between the retail price and what the client paid.
Afterwards, you can still see to use custom plugin to implement your own processing algorithm but I can't provide you any guarantee. Specially if you do have multiple currencies or if your product prices could change
Since HikaMarket base the processing on the "order product price" and even if the product changed, that information not. So you are sure that the processing is consistent. In your case you would have to do extra stuff to be sure to not change the vendor fees if the product changed or if the product is deleted.
2 - I'm sorry but I don't understand what you're talking about.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.