One option you have, apart from eBay ads, is google adwords - you can use google advertising for an eBay store. BUT it sounds as though your messages to buyers will be putting them off. It's best to take the 'innocent until proven guilty' position - don't accuse potential buyers of being unreasonable before they've even engaged with you!

I've found eBay buyers to be very honest and to respond well to your being honest with them - tell the truth if you are likely to be late sending, etc.. It's amazing how reasonable the average buyer is, given a bit of positive communication from your end.

Another thing I've found which may be useful to know is that a lot of my buyers hop onto eBay at lunchtime and seem to call up 'newly listed items'. Listing things late morning, and as frequently as you can (every day if possible - even if the items listed are small and insignificant)seems to increase traffic through the store.