Can you link to your site so we can take a look live? I know that certain fonts look pretty bad even in Chrome but its just the nature of the google fonts (not all of them render well).
For the greyscale, make sure that in the template builder template for that page the Image hovers effect is set to Greyscale. If it, try removing that element from the template and saving the template. Next re-add in the element and add your images to it again.
Additionally, you can try regenerating your thumbnails with this plugin: http://wordpress.org/extend/plugins/regenerate-thumbnails/
Without looking at the site live I can't say what could be happening with the portfolio in IE and FF.
If you have any plugins active, deactivate them as well just to make sure there are no plugin conflicts or code conflicts. If you are not using Angular 1.6, re-download the theme files from your downloads on Themeforest and re-install the updated theme on top of the old one just like you first installed it. That will help rule out any old bugs or issues with wordpress updates.