With $800 for casual selling fees in a month, opening a store would be the best option to reduce fees, so before anything else I would seek whatever permissions necessary to try and get one active. Your multi-quantity listings must be costing you a small fortune - without a store, the insertion fee is $1.50 per item, so for a quantity of 10 priced at $50+, you'd be paying $15 for every 10 day listing - $45 a month, as opposed to 20c a month if you had a store. 

If you can't open a store under any circumstances, I would suggest you consider how many of those items are likely to sell in 10 days, and only list that quantity. (eg, if you sell one or two per 10 days, only make two or three available for each listing - it's pointless to pay to list a quantity that won't sell in ten days). 

There is very little else that can dramatically change your fee structure, aside from using several IDs to take advantage of 30 listings per month with 0 insertion fees (you still pay final value fees), but it's not really the ideal solution.