
A Small Diameter Bomb moving at about Mach 0.85 has roughly the same kinetic energy as a 120mm kinetic energy penetrator round (~5.5 megajoules), but exerts that energy over a wider area due to it's size. On the other hand though, it does also have a 93kg warhead, which will obviously do some damage. Would a SDB kill a T-14's crew? Hard to say, but I'd lean towards no due to the unmanned turret. Would it disable a T-14 and render it combat ineffective? I'd say it would.
As for hard-kill countermeasures; I'm not entirely up to speed on the T-14's active protection system, but if it has protection designed to detect and defeat top-attacks, then it's definitely possible that it could significantly decrease the effects of a SDB against it by causing premature detonation. Again though, you're still likely looking at ruined sensors, set-off ERA and possibly a damaged barrel.
Against larger munitions (1000lb or 2000lb JDAMs) or bunker-busters though, the tank is screwed; having one of these go off a few meters early isn't going to help you much. Of course, using a 2000lb bomb on just a tank isn't exactly ideal, but it's an option in a worst-case scenario.
As for DIRCM; the T-90 has dazzlers, but they're pointed towards the horizon and aren't directed (they're the red-looking lamps / 'eyes' on the T-90, either side of the barrel). The T-14 has no visible dazzlers or DIRCM, likely due to faith in it's hard-kill protection.
*Edited