KoduStore makes marries objects and LevelDB UWP in a delightful way. It's a really basic document store with support for primary and secondary index support; this will solve most of your problems. Right now it's a PCL (for UWP).
Install-Package KoduStore -Version 1.1.0
dotnet add package KoduStore --version 1.1.0
<PackageReference Include="KoduStore" Version="1.1.0" />
paket add KoduStore --version 1.1.0
First stable version with public test cases and stable API