Burt's outie husband is a completely different actor (or at least has a radically different appearance in Season 2.
The Lumon severed floor lacks mechanical, electrical, and fire protection features that would be found in a modern real-world office building, such as sprinkler heads, firefighting hoses, fire alarms, electrical outlets and panels, exit signs, clearly marked stairwells, and HVAC vents (the one realistic element is the occasional fire extinguisher). While it is unclear if this was done deliberately, the absence of these elements enhances the otherwordly, isolating feel of the sets.
Besides "Helly R", the other Severed characters are referred to on by the first initial of their real last name, Mark "S" , Dylan "G". As Helly is Helena Egan, there's no explanation provided as to why she's Helly "R". All the non Severed employees know she's an Egan and the Severed ones wouldn't so there's no explanation as to where the "R" came from or what it means.