Intelligence is raised to 14 so that the option to use hidden weapon is available, like the effect of invisible air on Sabers' sword in fate/zero.
Other rings worth picking up for this build include hornet ring for post-parry ring swapping, the DWGR for more I-frames and RTSR to equip when under 20% hit points.
Blade of the Darkmoon is not the most efficient covenant for invasions, however I feel that it fits the roleplay the best as Saber fights with honour, like that of a darkmoon blade. Also this covenant grants access to DMB with 10 souvenirs of reprisal, which is more powerful than SLB, however I felt that sunlight blade fits the golden colour that is given off by Excalibur better than the blue given off by DMB. Sunlight blade is also allowed to be used in any covenant, so instead of staying in the darkmoons I suggest that you either join the darkwraith covenant or the forest hunters covenant and invade through their mediums.