Is wordpress big enough for my project [closed]

About OOP Themes) There are dozens of Theme- & Plugin-“Frameworks” out there. And some are OOP.

About custom coding) You could also try libraries like WP Alchemy for meta boxes and custom content. “Rilwis” offers another one. Then you could use some front end code to insert stuff into Custom Post types.

About “Jobroller”) You should post/ask your Q about “Jobroller” in detail at their page. Furthermore is it hard to know if it’s a) commercial and b) you didn’t explain your needs in detail.

About WP & Performance) Take a look at this Q for a more in depth look.