Nope, A BC will not not effect your 'to hit' with a CC weapon, BUT it will significantly decrease the amount of time it takes to get a target lock, so even on a pure CC titan like the Duellist it has it's uses.
Power does not corrupt; It merely attracts the corruptable.
For a CC based titan, IMHO you're best off going with a basic computer and good scanner and ecm. Even for ranged weapons, esp. machine guns, you're mainly going to use them at point blank range in any case so your to-hit will be very good anyway. Top of the line scanners are good to have, as you can scan while closing range, and a green scan really helps for those called attacks to the head with power axes that make close combat so darn fun.
Threat level is basically how many enemies are locked onto the titan. It might also depend on how big those titans are in relation to you and whether they have scans. I don't tend to pay much attention to it, personally.
Threat level calculation involves your ECM's quality (can't calculate it without one), your Battle Computer and your jock's Electronic Warfare skill. The formula? Only Larkin knows, and he is on vacation.