Looks like you are using one of those page templates starting with name “Portfolio …” (see attached screenshot). You just need to use the one named Default Template for these pages since you are manually inserting the portfolio entries.
The image sizes look fine to me. If you need them to be smaller (like those extra row below that you plan to get rid of), you can increase the value of parameter number_of_columns=3 to 4. Do let me know if you have trouble. A temp login to your site will help. Thanks