this is neat, but the wording is a bit funky and unclear. To fix this, say something along the lines of "any spell you cast that requires an attack roll and targets only a single creature is considered to  be an finesse weapon for the purposes of landing a sneak attack"

futhermore this spell does not seem to make an distinction between spells that need saving throws and spells that require attack rolls, nor against spells that require damage rolls. Do i still need advantage on my attack roll, or have an ally within 5 feet and no disadvantage to land the sneak attack? can i add my sneak attack damage to an spell that deals no damage, and if so, what damage type is the attack? Is this an feature like the swashbuckler rouge that lets you trigger sneak attack in a new wat or something else?

overal i rate this feat 3/5, you tried and you did well, but this is not all that great or even near the standard of most official feats in terms of clarity