I alleviate the "hacking takes forever" portion by allowing people with extended tests to roll "in the background" until they reach the threshold. Or getting them to roll once & divide the threshold by the number of hits, this is now how long it takes to accomplish the goal (hacking, lockpicking, vehicle repair, weapon modification).
This isn't always the case, it depends on the current pacing, how interested everyone is in the outcomes, level of risk, etc.
As to combats where the party is split up & not everyone is involved, while there's no avoiding it sometimes, I generally take a card from movies & TV and have something requiring initiative happen at each site, simultaneously. No one seems to mind that the devil rats in the sewers appear to be coordinating with the guards in the alley, since it means everyone's engaged & part of the action.
Obviously, these strategies don't work every time, so you'll sometimes have one group sitting and waiting.