There have not been many, to my recollection, that used the Feywild as a backdrop. There was
Beyond the Crystal Cave (WotC). This one is a D&D Encounters adventure which might not fit the bill for what you are looking into (lower level & Encounters format). On the flip side it was written by Chris Sims and Steve Townshend who were two of the best 4e adventure guys. There was also
Courts of the Shadow Fey (Open Design), which has a lot of awesome content for encounters and intrigue between the shadow fey and is an awesome adventure but it is a bit higher level than what you mentioned, and is really located in the Shadowfell rather than the Feywild. But any of that can be easily amended. It just depends on how much work you are willing to do, and how closely you want to steer to the WotC frame for the Feywild.
However, there have been some good resources that can be used to give depth to the fey realms and create your own adventures. Of course
Heroes of the Feywild (WotC) has a lot of good content to be used as inspiration for creating the Feywild. There was also
Nevermore (Expeditious Retreat Press) which is a setting book for the Realms of Dreams and Nightmare, which I have freely mined for many ideas for the Feywild. And you can also check Rodney Thompson's treatment of one of the important sites in the Feywild,
Mithrendain.
I have adapted many things for use in the Feywild as my group has been heavily involved in that location since about sixth level. Among other sources of inspiration for my Feywild campaign I've used
Labyrinth,
Legend,
Wizards,
Fire and Ice,
The Dark Crystal, and
Nausicaä of the Valley of the Wind just to name a few.