I have tried multiple ways of adding CSP and other security measures to my .htaccess, but I was wondering if this is the best way to do this. I can't seem to even get it working with the .htaccess file.
You may want to take a look at https://content-security-policy.com/ for examples.
For Apache, you should be able to use the following in either your VirtualHost or .htaccess file.
Header set Content-Security-Policy "default-src 'self';"
There's also an example by HTML 5 Boilerplate, which is set in the VirtualHost.
<IfModule mod_headers.c>
Header set Content-Security-Policy "script-src 'self'; object-src 'self'"
# `mod_headers` cannot match based on the content-type, however,
# the `Content-Security-Policy` response header should be send
# only for HTML documents and not for the other resources.
<FilesMatch "\.(appcache|atom|bbaw|bmp|crx|css|cur|eot|f4[abpv]|flv|geojson|gif|htc|ico|jpe?g|js|json(ld)?|m4[av]|manifest|map|mp4|oex|og[agv]|opus|otf|pdf|png|rdf|rss|safariextz|svgz?|swf|topojson|tt[cf]|txt|vcard|vcf|vtt|webapp|web[mp]|webmanifest|woff2?|xloc|xml|xpi)$">
Header unset Content-Security-Policy
</FilesMatch>
</IfModule>