If PivotX serves your needs, you can probably use it for 2-3 more years without other problems than what you have already experienced.
I've found other strict errors while editing articles (e. g. inserting pictures), which were not hideable with the php.ini. (?!)
So I had to change the code in lib.php/makeUploadFolder:2704 and Smarty_Compiler.class.php/_compile_file:400.
SQLite, a single file database (no server needed), which is included in all recent versions of PHP.
I wasn't sure of that! So it's a real hope to switch to Bolt...
There is an incomplete upgrade path from PivotX to Bolt.
... in (hopefully) near future.
BTW: Your "SourceForge donation page" is not working!