I think you are wrong the Uchiha was strong they had many elite ninjas such as :Shisui Uchiha, Itachi Uchiha, Fugaku Uchiha ( since he was a leader it means that he was strong) and many others. The Uchiha shouldn't be underestimated cause if they were weak the Village Elders wouldn't order their wipe-out, the Uchiha would have won the war, no doubt about it.
Many equals three? Shisui could mind control- one on one and once in a day ( as Danzou said) = big deal and would have helped a lot.
Besides Shisui was dead within 6 months of Itachi joining Ambu ( Itachi was11) The massacre took place after he was made ambu captain at 13. Shisui was asked to spy on Itachi. I doubt Itachi would have fought along with Uchihas as he was a nationalist and Shisui's eyes were already with Danzou.
Fugaku Uchiha = might have been a fine warrior but don't forget that no Uchiha since Madara was known for extra ordinary talent till Itachi.
Besides rest of Konoha is not build of weak shinobies. Hyuugas, Nara clan, Aburame The third Hokage everyone had talent to compete and answer back.
Madara was lurking in the shadows. whether Uchihas won or lost he would have jumped in to wipe out the remaining ones. And the other villages would also look out for bounty grabbing.
It was a lose lose situation for Itachi. He chose rest of the village over his clan, thus containing the tragedy in smaller group. He knew Madara won't let the clan go easily and sooner or later he would strike both. He let him strike one in exchange of giving more time to the village- hoping that village will be able to gather itself and be ready when Madara makes its final move.