If you write your own code you don't "have to" stop using FrontPage. You can continue using it as a text editor. However, before turning off the FrontPage Extensions on your server, you must remove all the features in your site that require them. After you turn off the FPE, you'll switch to FrontPage FTP publishing rather than HTTP. There's not much practical difference between the two. It's a different setting in the publishing options dialog box.
I've been introducing javascrpit and php.
You can write JS and PHP yourself in FP, though other design programs might give you more assistance doing it.
The only things I actually use Frontpage for are the includes.
PHP includes are better, but FP includes don't require the Extensions and you can use them even after turning the FPE off. Here is a list of the things that require the FPE: [support.microsoft.com...] .
I want more freedom in places like .htaccess
It is installing the Extensions that creates the .htaccess file you listed and that makes certain .htaccess features unusable. Once you turn off the FPE, you can do anything in .htaccess you want, while still using FrontPage to edit and build your site.
and I don't like Frontpage spitting out less-than-good code.
If you stay away from the webbots that require the FPE, FP code is good HTML, and easily validated.
The following code is ok even in a site that doesn't use the FPE. You can use it as a starting point in your new .htaccess:
and I'd like to add something like: AddHandler application/x-httpd-php .htm .html
Question: Once I remove FP extensions, will the AddHandler line work? Right now it don't.
There are some variations of that line, different ones for different server configurataions. Ask your host to be sure you are using the right one. I started using PHP in .htm files before turning off the FPE, and had no problems. However, I do admit that I had installed some mods to my site that allowed certain .htaccess features to work that ordinarily don't in a stock FP Extensions-enabled site. I don't remember if this was one of them.
2) I am pretty sure I can remove all the _vti folders. What about _private?
After you turn off the extensions, you can remove those, and you should remove _private. The Extensions won't be protecting it anymore. You can create a replacement private folder of your own, protected by an appropriate .htaccess file.
3) Is there anything else to be aware of other than checking any other FP features to alter/update?