My issue is that reflector can be jumped over pretty easily
Not from a short hop, and not when they're trying to dash in to attack or grab, will this matter.
if they do so, you will get punished as it has notable end lag
It's really not that bad, no worse than Phantasm endlag.
Is it the kind of move that you only use at max range? If they are close enough, they can still hit you even if you hit them.
Really dude, you should give it a spin against CPU opponents to test this out. Dedicate some matches to relying heavily on Reflector as an attacking move.
Yes, you should be trying to hit with as far of it as you can, but even then you might still have leeway to throw it out when the proximity is greater depending on the character you're facing's capabilities at those ranges.
The goals with using the Reflector are many. One is to have the largest hitbox you can get out to fight fire with fire---your limbs can't compete with swords, and nothing else in his arsenal can. Another is that the Reflector has stopping power. It makes your opponent think twice about what to do next after they get hit. A third is to slow them down and frustrate them, causing them to throw out moves of desperation which you can read and punish accordingly. Bait out a dash attack after hitting them with it couple of times, and shield grab them, perhaps. You can even use the Reflector when trying to recover to the stage when the opponent is camping the ledge.
You need to start practicing its use to get comfortable enough to discern its practical usage. I am describing it very accurately, but it's easy to disregard its effectiveness in theory if you've hardly seen or experienced it in practice, what with its apparent weakness and unpopularity as an option.
I think I try to keep my distance because I'm trying to find an opening.
That's not the best mentality to operate under, because you aren't playing a character like Fox that can capitalize on mistakes at that range. As Falco, you have to create your openings. But you absolutely cannot do this without taking advantage of his special moves.
Lately, I sometimes feel I'm too aggressive with my approaches.
I don't think aggressiveness has to do with it. You might just be trying to play Falco with a style that assumes he's some other character. I've seen this happen with other Falco players like Osiris197, with whom you very much share a style.
That's all I really can say for now between this and your other thread until you've tried what we've recommended and figured out how it works.