Feeding many hungry birds sustainably, naturally and cheaply - if at all?

Hello. I am new here, but I have been running a five-star bird restaurant for several years now. The menu includes (all from the RSPB shop), peanuts, black sunflower seeds, sunflower hearts, table mix, and suet balls. I use a bird table, suet feeders, and seed feeders containing nibbles, dried mealworms and kibbled peanuts. My hungry customers get through a lot quickly. One clear example is the suet balls, 150 of them gone every four days. I normally only buy when there is the offer of 20% off, but nevertheless I am spending hundreds of pounds every few months.

My take is that because humans have destroyed so much natural habitat and the feeding opportunities along with them, that we have a responsibility to help those we have hindered. However, am I too generous, topping up the food whenever it gets low (several times each day), and perhaps stopping the birds looking for wild food?

Is there any wild food for birds out there these days?

I worry that by being generous, the birds breed more than they would if I wasn't feeding them, and then the offspring also come to rely on what I am putting out?

I question the naturalness (and sustainability and ethics) of feeding the melted fats of animals that most of these birds would not usually have the opportunity of feeding off in the wild?

I appreciate birds love fat, and so they like peanuts, but I expect these are flown in?

If I were to substitute the suet and peanuts with growing my own mealworms, would I be able to grow enough to satisfy such a hungry clientele with only mealworms and seeds on a daily basis? Does anybody have experience growing a large number of mealworms, and if so, how do you do it?

I would be interested to hear from people who have a good idea of the facts. Thank you very much.