Textastic internally uses libcurl, which uses binary transfer by default.

For now, you can drag the file icon from Textastic's window title bar onto the Safari Dock icon to view it. 

The Mac version does not have FTP functionality at the moment.

Yes, that would be possible to implement, but isn't yet available in the current version of Textastic.

You need to create a folder called "#Textastic" (with a capital "T"!) in Local Files yourself.

You can find more info with screenshots in the manual at http://www.textasticapp.com/v5/manual/lessons/How_can_I_add_my_own_syntax_definitions__themes_and_templates.html

In general, the auto-correct feature in iOS does not work with hardware keyboards, but only works with the virtual on-screen keyboard. You can try this in any other app like Apple's Pages or the iOS Notes app.

Fortran is already supported. It is also listed as a supported language at http://www.textasticapp.com/v5/manual/lessons/Which_file_types_are_supported.html

This sounds like a useful addition. I don't have plans for an Android version of Textastic.