while i applaud your resolve and the fact that you were creative in trying different things before posting. i think you sell yourself short in saying x won't work for y reason i tried and w won't work for z reason i already blank....
what i mean to say is that there is something to be said about tenacity and being downright stubborn. i used to be in professional sales (and very good at it, people almost don't believe that kind of money i used to earn and walked away from when i quit the corporate scene cause i my heart just wasn't in it. i joke now and say there wasn't enough applause lol...i only mention to add some validity to my experience with rejection), one of the things that really distinguised the successful reps with great numbers was an almost uncanny ability to be deaf/oblivous to 'no', no is hardly ever no, at least not the first time from the first few people you get in front of in an organization. keep kicking over rocks, it really can be a numbers game, in one industry the average was 100 approaches,30 might be willing to listen, 10 were good prospects for a buy, but a buy could be immediate or months or years ago way you you keep feeding the prospects thorugh and filter and keep on.
part of the trick with these 'impenetrable' organizations is the need for a 'favorable' introduction, unfortunately you really do need an 'in' or referral in order to get in front of the decision makers. consider fiding ways to go to business networking mixers, etc. shakes hands, that sort of thing.
more immediate results can probably be had with again looking ot raise funds if necessary to simply bank roll it yourself. that is find a free lance conductor, free lance pianist, free lance string players, etc. find a venue, book it, market it, etc. and just put the thing on the stage yourself. again 'broke college musicians' will be a great place to prospect. get a good turn out or review and people may start to take notice.
continue to think about ways to get in front of people that believe in this, you might be surprised who you meet or get referred to. now that it is summer soon, try to approach conducting or composition professors at the schools see if you can meet with them during their office hours (they are usually required to keep these even if they have no one to meet with by many university policies, etc.). see if you can un pack your case not to ask them if they will do it for you but what they would reccommend to you to do if you were their student, etc. i think you will find a sympathetic ear or two this way.
many large churces have pretty decent instrumentalists working for them. consider looking to see if you can put this on in collaboration with a church, many times they are looking for a way to reach out to the community and get new people into their seats without immediately turning people off iwth a 'religious' event. you can get a nice venue, piano, etc on board this way, again you may find speaking to a preacher/minister of music, etc is a lot easier than some corporate jerk.