Practice and train for whichever perceived threat as best as one can. With the OP's analysis, it is prudent to start with the statistically close encounter.

Later, whether a day later or years later, consider getting whatever lower-light training which may include night-sights and/or weapon mounted lights. Now you'll have a choice (with an educated investment in more hardware) and have the knowledge to make a much better-informed choice.

The OP seems to be constrained by not wanting to buy a different gun. That's fine with me and I don't recommend getting rid of a handgun a person is already very comfortable with handling. If a person can't afford or doesn't want to try a gun with a light rail, with further expenditures in night sights and lights (I've got zero experience with lasers and they weren't authorized where I worked) that's a personal choice which easily can end up in the $1,000 range. It's not up to me to tell someone how to spend his/her money and this is just for the hardware; not any training to benefit the hardware.

What exactly was/were the question(s)?
Are night sights necessary? The can't hurt, but I haven't put them on all 15 handguns I own but do have a few which have night sights should I need them.
Is a weapon light necessary? That will also depend on one's training & experience along with the liklihood of being in darkness. I've got ~5 weapon-mounted-lights (WMLs) leftover from being a cop and my training involves also carrying a handheld light. The handheld light is the bare minimum and this training predates the WMLs.

"Blues7" seems to have the most experience using lighting and has the best advice. I say, at least, get one or two good handheld flashlights. I like the Streamlight and Surefire brands, but there are others. Later, consider night sights and a WML (again I've only got Streamlight and Surefire, but there are others; the two brands I own were the only brands OK'd for where I worked).

I admit, I don't change over to a WML'd handgun just to go out at night. I do have a flashlight on me even during the day.

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