I second the BCM/Vltor Gunfighter Model 4 charging handle. For comfort and strength this has the middle size finger latch but you could go with the Model 3 if you want even larger.
For triggers we need to know more what you're looking for and price.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek