1. As Nils said - the Comment Preview is the only possible solution right now. We/I am working on massive template changes for 4.1 that need to be done to allow this sort of thing (and many other exciting new layout capabilities)
2. [Looks up Aristeer 2] hmm a template generator ... ok, can you explain this a little better with a screenshot maybe? I don't know which margins you mean.
3. Yep, you can change most things on/off in the backend. Again, this is all being reworked so that every part of JoomlaComment has it's own ACL's. If you feel like it, you can edit the HTML of your template yourself and just remove some tags. Here are some examples:
Delete this to get rid of the Website field:
{BLOCK-_ENTERWEBSITE}
<div>
<label for='twebsite'>{_ENTERWEBSITE}</label>
<input name='twebsite' id="twebsite" type='text' tabindex="3" value='{website}'/>
</div>
{/BLOCK-_ENTERWEBSITE}
Delete this to get rid of Title field:
<div>
<label for='ttitle'>{_ENTERTITLE}</label>
<input name='ttitle' id="ttitle" type='text' tabindex="4" />
</div>
...and you get the idea. Some things have BLOCKS, some don't. If you can turn something off in the backend though, it's better to do it there instead of hacking-out the JoomlaComment template
P.S. Don't hide the E-Mail or Notify or Name or Comment, or (unless you have members-only comment viewing/writing) security because those are more-or-less required for things to work.
EDIT: P.P.S. Removing tags might result in JavaScript errors/warnings when someone submits their comment but they are usually silent. If there's a popup or an error after you remove a tag just let us know right here