Creating Offline Data Entry Form

We have a client who is using an Access 2013 DB (Office 2013 Pro Plus) with the Windows 10 operating system. They are working on implementing the infrastructure for using Office 2013 under the Office 365 subscription. The Access DB they are using is setup as 2 .accdb files, one that contains the back end data, and the other the objects for the UI.

They will soon be using MS Surface Pro tablets for their field personnel, and want a form that can be used for data entry while in the field.

We talked about creating a form that could be used offline (basically a new FE and BE) and routine that would do data synchronization back to the network database when submitted by the field personnel.

From online research, it looks like this may be better solved with the use of Office 365, SharePoint, and Access Services. Unfortunately, since they haven't yet migrated to Office 365, we have no way to test it and need to determine if it is a viable option, or if we will need to do the "custom routine" option. Since they are planning to migrate to 365 anyway, if it works, it would obviously be a more cost effective solution for them.

Here are a few questions we have when considering this solution:

1) The Internet is not always available in the field, so the solution must be one that can run offline. Is this possible with 365?
2) They are working to get Sharepoint Services working soon. It looks like we will also need them to implement Access Services. What do SPS and Access Services look like, how do they interact, and what features do they offer and how can we leverage them?
3) What does the web-based Access application look like? What is the path to convert/migrate an Access 2013 DB to a web app? Does all development need to be done (or redone) in a new dev environment for 2013 web apps?
4) The "hydration" of an offline copy of the form is what we would need to distribute to an offline tablet device. What does this involve? Is a small footprint .accdw created? What happens after that when first accessed by the user? Is there a hydrated .accdb for the Front End and/or Back End?
5) If we must hydrate the entire application, we may need to implement security at that time. From our research, it appears that once the Access web app is published to SPS, the objects (lists, etc.) in SPS are lockable at the SPS level, and we may have to use that security layer instead of Access security, correct?