After reading what Kiki said I don't know what to tell you.
I was going to say that whatever you do, don't start off with stevia. It's really hard to make the cold switch over to that stuff!! Where as splenda, for the most part, cooks like, acts like, and tastes (mostly) like sugar. It does however have maltodextrin in it.
I've tried xylitol (bad for dogs I think) with mixed results, and coconut sugar, which is more like brown sugar, but splenda is about the only one that will give you a passable cookie, zuicchini chocolate cake, and homemade strawberry sorbet.
I'm sure there are some good ones out there, but we live on a budget so paying $15 for a tiny thing of sugar replacement is not on the menu for us. Kiddo's baked goodies get real sugar and I'm good to steal only one cookie or muffin.
I'm not sure without seeing a picture, however if you mulch over the top with something light, it should keep the moisture in and prevent the crust as you describe it. My other farm, more northeast-ish, had crusty brown clay like soil. Mulch did wonders for it plus it's just good gardening practice for happy plants.