Document management system

I currently have a Filemaker solution that I would like to convert to a different format. Its based on online form management with a few features to control who can view, edit or delete forms. Also, their is an approval process, based on user role. A form creation component will be needed to add new form type and form fields in the future. Remote and on device signature capture will be required. Forms will be related to client's profile, this is not for marketing purposes. We are a small therapy office, so all forms will be related to a client's profile. When searching forms (multiple types of forms), results should appear in one list, NOT on separate tabs or something. System will require multiple search criteria (ex: Client Name, Date Range, Status, Author, Form Name, Service) where the user can use one, or a combination of search options. Certain forms, when approved, will reset certain due dates. We also work with "units", a number used to determine the amount of session hours. Units are based on a calculation that is unique based on the client's service. We have a treatment plan form that requires a section of questions to be created in a parent, child, sub-child relationship. With he ability to have multiple childs under one parent, and multiple sub-childs under a child. We also require signature capture. Signature will need to be remote, via email link as well as directly on the users device. We also require an API connection to our billing service. The API is already created and supplied by the billing service. Our goal is to move away from filemaker to another format that can be hosted on our Hostmonster account.