@SteveITS
Yes, by "lockout" I mean exactly that. Couldn't access the web interface, connect through SSH or even ping the machine until packet filtering was manually disabled.
At that time there weren't any firewall rules except for the anti-lockout rule which is present on the LAN interface by default if I remember correctly.
It was only after everything finally worked as intended that I started creating my own firewall rules, and from then onwards everything's been working fine. :-)
My best (and honestly a little uneducated...) guess would be that my self created interface mismatch prevented me from connecting to the pfSense machine.
I suppose the lesson here is that taking shortcuts such as the one described here can't be relied on. No more trying to rename interfaces on pfSense / FreeBSD.
On the bright side, no interfaces have gone down since performing a fresh installation and I sure gave it something to chew on.
That's with the default RealTek kernel driver, by the way, the same one that kept acting up in the past and which prompted me to try the alternative v1.98 driver.
For lack of a logical explanation I suppose we can call that a lucky coincidence.