It might not hurt to make a few tweaks to this spell to keep it in line with others of the level you're shooting for.
Having it be 5th-level puts it in line with Mass Cure Light Wounds, which is 1d8+1/CL (max 25). But that's healed per person. Now, it can affect up to 1 target per caster level, so let's assume a caster level of 10. That's 10 creatures each being healed 1d8+10 hit points. Now they'd all have to be gathered within a 15-foot-radius, which is sizable, and you can select the targets individually.
With making Healing Spark a series of orbs, those could potentially target multiple creatures or the same, and it could target them in a far wider spread. The base spell on its own probably shouldn't be a 0-level spell, and should probably sit at at least 1st, but that's not what you're looking for. An easy start would be removing the 1d3 healed, as it feels a bit unnecessary. Having a flat healing of +1/CL at our assumed CL 10 puts that at 10 hit points per orb, and the proposed 1 orb/2 levels puts us at 5 orbs, which is the equivalent of 50 hit points, which is pretty notable on its own.
The source spell doesn't list any actions for controlling the orb, so we should assume a Move action for that, which falls in line with most duration spells with a movable effect. That could control all of the orbs simultaneously. Now, to try and keep such a spell balanced, a CL cap on the orbs would make sense, so you don't eventually heal someone 200 points with a 5th-level spell being cast at CL 20 (10 orbs for 20 HP apiece), which would heal more than the Heal spell, which is a 6th-level spell - and at a range no less. Having a CL cap would make sense for such a spell to help limit its power. Alternatively, making it so a creature cannot be affected multiple times by the same spell also makes sense. So you could say a single creature can only benefit from a single orb of the spell. You might even be able to push that to one orb per round, but again, having that CL cap on the orb would be recommended on that.
Hopefully this will help point you in the direction you're looking for!