Congrats on getting to Hell! Always nice to see a Conqueror happen
I will basically just echo jiansonz's statements, as he pretty much nailed it.
1. Do you need to get the kills? Your merc/grizzly should do the trick just fine.
2. Do lots of gambling and shopping for alternative gear in the slots you feel are weak. For examply, you should easily be able to shop a Plated belt with decent single resists (up to 30%) and high life (up to +100) - ie. Coral Plated Belt of the Whale. As jiansonz said, at least a partial switch from MF gear is advisable at this point, and will make a significant difference in your survivability.
3. Treachery armour for the merc is probably your best option for that Lem, as a safe and living merc is a very valuable commodity in HC. As for his weapon, you can always try rolling a Cruel one for him, or else you can keep a sharp eye out for elite bases and socket them with the cube, then look at RW options. Calabi's merc finished the game with an Insight CV and that was more than enough.
On that note, do you have any other useable runes? Lionheart is another option for the merc's armour to beef him (or your druid) up if you want to save that Lem for something else (although I'm not sure what at this point other than maybe Lawbringer on an A5 merc)
4. This is tougher for a druid. Like jiansonz said, you can switch your merc around to try and accomodate this. Another option would be to shop a bow that has ctc amp on it, and keep it on your switch for those situations. Then you can plink away from behind your helpers and break the PI's.