Whitelist full URLs in HTTPS traffic with Privoxy

Question

I managed to configure Privoxy to intercept HTTPS traffic:

• generated CA and certs in Privoxy
• configured Firefox to use the proxy and installed the CA cert
• FF reaches HTTPS sites transparently through Privoxy without any problem.

Now what I want is block all HTTP/HTTPS traffic, and just allow ONE HTTPS URL (not one domain, one full URL).

Here's my configuration:

/etc/privoxy/config

# Commented out existing config to have the minimal thing:
#actionsfile match-all.action
#actionsfile default.action
#actionsfile user.action
#actionsfile regression-tests.action

# this included file is recognized, because it has an impact on my test
actionsfile myrules.action

/etc/privoxy/myrules.action

{ +https-inspection -block }
acme.org/urlthing

{ +https-inspection +block }
/

Nothing works, all site are blocked, whatever I do. I tried infinite variations of the above (removing/adding block or https-inspection, changing + to - as you don't know what it really does...)

Of course, there's virtually no example of a working configuration online.

Any help appreciated, thanks in advance!