In this case it is better not to point the url to the field folder.
What works is: pointing the url to the folder which contains BoltWire and fields.
Then use htaccess to redirect the url to the field.
RewriteCond %{HTTP_HOST} ^(.*)mydomain\.com(/|$) [NC]
RewriteRule ^(.*)$ /myfield/index.php?p=$1 [QSA,L]
Now you can edit your site. But BoltWire keeps rewriting all links to "mydomain/myfield/xxx".
To get rid of /myfield/ in BoltWire I shortened $fieldURL in index.php of the field to
$fieldURL = dirname("https://$_SERVER[HTTP_HOST]");
As I said, that hoster is problematic.
Greetings, Martin