Ebay are lowering our selling limit day by day lower and lower each day going down lower

The best way to get your limit increased would be to sell up to your limit and dispatch orders promptly. That way eBay will probably raise your limit. 

You can't rush it and if eBay says you're not eligible at the moment, you're not eligible. Keep on selling steadily and hopefully you soon will be.

What is your limit anyway? You've only received an average of three feedbacks a month for the last year, so this can't be what's holding you back. Your limit must be higher than 3 items a month, surely?

If eBay requires you to register as a business seller you will have to do so, unless you can successfully appeal this. It's eBay's site and their decision.