Specific Media Settings & Regenerate Images Sizes

I made a convert from joomla to wordpress, the photo now is ‘featured image’ on wordpress every corresponding post that it took from joomla, has the size 600×300. So, at the “settings-media” I choose as max the standard size to be 610×305 of the theme I have so it won’t with it’s design, min 270×135 and thumb 130×65 that is marked with this “Crop thumbnail to exact dimensions (normally thumbnails are proportional)” with this on, it crops the photos instead of resizing? Because I want the resize.

The photos are taken from a specific folder (old-photos). Even though, “Organize my uploads into month- and year-based folders” is marked.
Obviously, because there wasn’t any other way to take the standard(600×300), it changes the dimension on a html scale, whenever it asks to be displayed correspondingly with the sizes above, causing of course the site to go slower…

1. How can I fix this problem? I mean, to make the standard (600×300) 610×305(Enlarge them with no loss of quality) and the create after on the newly installed photo files (610×305) the smaller (279×135 &130×65) corresponding sizes.

2. Is it possible the height to remain undefined (Should I put 0 on the height pf every size at the settings-media?) and arrange the photos based on “Organize my uploads into month- and year-based folders” that is marked?

[No bumping, please.]