Your comments

I do plan to offer the iPhone version as a separate app. There are a few problems I'll need to solve, but the editor is already working well. It should be available in a few weeks.
Currently not. I'll consider adding import functionality in a future update.
See also http://webdesign.about.com/od/beginningtutorials/a/aa040502a.htm

  • links in the same directory as the page have no path information listed: filename
  • sub-directories are listed without any preceding slashes: directory/filename
  • links up one directory are listed as: ../filename

You can do that: just write images/image.png - you need to leave out the first slash. The slash would tell it to look at the root directory - just like on a real web server.
Please try to use the T-SQL TextMate bundle from https://github.com/adamv/tsql.tmbundle

Have a look at http://www.textasticapp.com/v4/manual/lessons/How_can_I_add_my_own_syntax_definitions__themes_and_templates.html to see how you can install it in Textastic.

The problem is that the iOS file system doesn't have file permissions like a Mac. On iOS every app has its own sandbox environment and there is no executable bit, as you can't execute arbitrary files. There is also no shell environment.

Adding chmod functionality for FTP connections is still on my todo list.
I'll have a look and try to fix it in the next update.