Which one is the Right Approach - Re Using Page Layouts or adding Web parts directly to pages instead of page layouts in SP 2013 online site ?

Hi Team,

I am SharePoint 2013 developer. Before asking question I would like to explain the requirement in clarity.
We are developing one O365 SharePoint online site which is having 10 different page layouts with different and some common webparts and we are reusing these page layouts by deploying a sandboxed solution which is having page layouts. These page layouts contain filter and query to display data using some condition and predefined values. By using these layouts we have to create 100+ pages. All pages will show data according to that page name and category (if it belongs any). We have not written any code to develop the site, everything is OOB feature.

We have used below feature/list/lib of SP Online 2013:
-Document Library
-Survey
-Calendar
-Lists
-Discussion forum library
-OOB Search feature

Now, I would like to know whether this is the right approach to reuse the page layouts. Or can we add webparts directly where the logic resides in the webparts and add them to the pages instead of page layouts?

Also how to deploy page layouts/pages from one server to another? Currently we are deploying everything as a feature using sandbox solution. 

Could you please let me know the right approach to follow. I am asking this question because we are facing below issues:
-Sometime page layouts gets corrupted, showing nothing.
-All written filters/logic disappear when we open layouts in Designer
-Deployment is pain using Sandbox solution

Waiting for your reply.