I would suggest playing the game naturally whilst using a Ghost shell mod to spec the stat split you're looking for rather than trying to farm lost sectors. Having farmed them for a fair few hours over the last weekend for all the exotic helms and chest armour on each class, I can safely say that RNG comes and goes in waves (for me personally). I had hours or zero drops to having 6 runs in a row provide an exotic, however in your position not only do you have the inconsistent drop rate to contend with but also the stat split you're looking for. This means you're essentially rolling 2 dice trying to get the ideal result on both rolls which is a hard ask. Playing naturally means you can work towards other goals whilst keeping an eye out for free drops like the exotics from ritual playlist activities and also Xur's weekly rotation of armour (Warlock helm this week rolled a 70 stat). Obviously this won't apply to you if the helmet you're farming for is a lost sector exclusive, but with it unlocked it will get added to the world exotic engram loot pool meaning it can be gained outside of sectors.