I am thankful to you, Richard, for your insightful guidance hinting at the inherent nature of the Portfolio design. I thought it should be now easier to sort out the display issues with my custom CSS editing tool. My every attempt however miserably failed, obviously due to my inability in identifying the needed theme-specific selectors.
To me, the most enigmatic theme behavior is its resistance to change the position of menu. I tried it without any success by all means that I know, even by removing the menu widgets, which should have displayed a horizontal menu at the top. The menu repositioning is a critical requirement for me; otherwise the menu growing vertically will soon go over the feature image located centrally compromising with its visibility.
I realize today that, the things are not so easy and smooth to change Portfolio look and feel, as I thought before buying the theme. It took much of my time for my content development activities, which is far more urgent for my newly created site. The only reason I had opted for the Portfolio theme is its capability of sorting items on its portfolio pages in any desired order, and not restricted to ordering by posting dates alone.
Are there some other WP.com non-blog-like themes (free or fee-based) that supports display of items by titles/ categories or any criteria and not by compulsive Posting Dates? If any, I would like to explore possibility of shifting to a more comfortable alternative before it is too late to go out with a refund. I badly need your help. Wishes - Asok