You won't get a limit increase if it's telling you that you won't, plus your feedback profile indicates that you've some real issues with selling.
You also can't sell mystery boxes on eBay, that's a policy breach against your account.
And you need to trade on a business account to be compliant (a private seller is one who is just selling off their own personal items such clothes from their wardrobe, bits from their loft/garage etc.).
