lol
can they be with clown loaches, given the loaches are big? im just worry that the loaches might be too active for the knife
A BGK would do fine with the Clown Loaches, you shouldn't have any issues.
can they be with delhezi polypterus? ive heard that ghosts nip at everything since their blind, r they really blind or just bad eye sights?
They should do fine with Delhezi, not positive, but if you're worried about the Delhezi I wouldn't be. As long as the Knife is larger than the mouth of the Delhezi, he should be fine.
They have bad eye sight, but are not blind. Had mine with a 5" Senegal Bichir for a year, no issues.
how fast do they grow? how long will a 60g last?
They grow very slow, and would be fine for years in a 60-Gallon. They grow fast up until around 8 inches, then slow down drastically. What I do know is that my BGK was at 4" when I first got him, and recently passed due to a filter issue at 8", two years later.
floating freeze dried shrimps, pellets possible as food? difficult to wean onto pellets?
Both food items have been accepted by BGK's once before. Not sure when mine started eating pellets and flakes, but I guess over time as I fed the rest of the tank flakes, etc. the BGK just started eating whatever food item was put into the tank.
if i turn my tank light off, but leave my living room light on, will the ghost come out?
It might work, but it might not. Worth a try.
Once mine started to get larger he was out for often.
anything i should know before gettin one?
They can be very aggressive towards specific species of fish, so tank mates should be researched before being put with these guys. Mine always had an issue with certain Catfish and Blood Parrots. 
also i have some 1.5" datnoids, the ghost im lookin at is 4- 5". good right?
As I have never had experience with Dats, I am not sure of that question. IMO, it would be a risk of them either nipping at the Knife, or opposite way around.