It is essentially impossible to quantify or measure the ability of the Borg to incorporate SW tech into their own base, becuase we don't know much about the assimilation process (aside from its zombie like nature). Simply assimilating alot of people is not a guarantee of gaining the requisite technical/scientific aptitude to reverse-engineer tech. They might be able to build SW stuff on their own by assimilating techs and engineers and stuff, but I don't think they'd be building Borg-SW hybrids without far more effort (hyperspace tech, for example, can be built and operated without understanding the underlying, fundamental principles behind that. THe borg would have to assimilate the right kinds of scientists to gain that knowledge.)
In voyagers final episode, the borg were able to figure out how the armor from the future worked within moments of assimilating the shuttle's armor. This should demonstrate ability to understand how foreign technology works without having to assimilate a designer of the technology. I'm sure information about conventional technology's design would be located in the death star's computer records too.
Regarding Borg ship regenerative abilities:
The only time such abilities have been clearly demonstrated was in TNG:'Q Who?'. In ST:FC we saw a Borg ship with obvious damage that was not showing any sign of regenerating. Either-
A) The Borg cannot regenerate their ships in the middle of a battle.
B) The Borg have no actual regerative ability, and Q was doing it to put the scares into Picard.
We see a borg scout vessel giving the order to regenerate their primary shield matrix while in the middle of a battle with voyager here:
JANEWAY [on monitor]: Is it? You've scanned our vessel. You know we can match your firepower.
BORG [OC]: You will be assimilated. Regenerate primary shield matrix. Remodulate weapons. Security breach. Starfleet photon torpedo. Disarm weapon.
Plus in this episode Janeway says that once they disable a borg ship sensor array that it takes them two minutes to regenerate it.
CHAKOTAY [OC]: but we also picked up some uninvited guests.
JANEWAY: What was our time?
CHAKOTAY [OC]: Two minutes twelve seconds.
JANEWAY: Twelve seconds too late. Once we disable their sensor grid we only have two minutes until it regenerates.
Plus in best of both worlds part 1, here's what was said after they shelby's away team destroyed the power distribution nodes on the borg cube:
LAFORGE: Commander, reading subspace field fluctuations from within the Borg ship. Looks like they're regenerating, restoring power. They could be capable of warp any minute.
then it gets warp power back shortly after in best of both worlds part 2. A borg drone's ability to regenerate their body parts and components is seen in plenty of places like enterprise episode "regeneration", the medical applications mentioned and demonstrated in voyager episode "unity", and when 7 of 9 cut herself in episode "Revulsion" she said that as a drone she would have healed in seconds.
Again I figured they just missed an Implant that was still in him or something.
seven of nine could hear the borg when in close contact with a ship in episode "child's play" plus the queen borg communicated with seven of nine a number of times in other episodes
Uh no. They have a Death Star but they have nothing to supply or maintain it with save the vessels own stores and what they salvage from others. I mentioned before that they best haul ass to the Outer Rim and build a logistical base for themselves? I didn't say that for shits and giggles, without a means to maintain and supply themselves they have until something breaks that they can't fix or they run out of fuel/ammo/space food.
Now maybe they come across some system they can rape for resources and spend some time checking out their kit and figuring out what it can do.
the borg would use replicator technology for that and nanoprobes would do the rapair work.