WP Smart Image is deprecated. Please change to WP Smart Image II.
No. Using custom fields to show associated images is a wrong method. Yes, it is relatively famous, but is wrong. WordPress has a very advanced ways to control post's images. However, saying is not the same than do it, because many times it is some difficult to achieve tha we want in this area. WP Smart Images simply makes this work a quite more easy to you.
Noup. This plugins uses all existing post data you have been entered through WordPress Editor. Only creates a little field in options table to save your settings.
Just activate the checkbox for option "Activate editor box" through Settings page. Save your settings.
Absolutely not. Your old settings remains intacts.
Yes. Please read the first step guide of WP Smart Image
Yes, you can combine parameters without an specific order. Logically some parameters may not appear depending of your settings. For example, a "rel" attribute will not shown in an unlinked image, because "rel" is a property of links. In cases like this, if you set wrong parameters the plugin simply ignore them and works anyway.
You must to read the parameter's table to setting your combo correctly. If you have a Stric DTD site and if you activate a "target _blank", of course you'll ruin your standard. If you add a fixed ID's to several images or links, you are proceeding in a wrong way.
... and of course starting a new topic in WordPress.org forum.
Please let me know you're thinking through any of ways above. Thank you!.
All your suggestions are welcome. Thank you!.