As the Reigning Master of Sinanju he has amassed a plethora of feats, and I will also mention Chiun's feats because Remo has since surpassed him.
For evidence of that:
In Look Into My Eyes we see Remo Williams defeat Chiun in a single move.
In Father to Son he becomes the Reigning Master of Sinanju. Chiun assumes the title of Great Teacher.
Now since that's been established I will begin.
Starting with explosions and bullets?
Both Chiun and Remo are able to outrun a large explosion that destroyed a hillside on a mountain Quicksilver style, and the explosion is frozen in time compared to them. Remo again is shown to be much faster than Chiun. While Chiun could escape? Remo had already been long gone by the time he did that. This to the point that Chiun had thought that Remo had been caught in the explosion.
Taken from Air Raid.
In Prophet of Doom we see Remo Williams move so fast that he can create whirlwinds of compressed air that can intercept and deflect bullets.
In 100 Proof we see Chiun treat reacting to bullets as a trivial thing. He is able to effortlessly flick seven bullets out of the air at the same time, and use said seven bullets to flick another seven bullets out of the air that were heading towards Stone (Remo's son). As I said before your average Master of Sinanju is basically Quicksilver. And even bullets are basically stuck in a time-stop when compared to them.
In regards to electricity and lightning bolts?
In High Priestess we see Remo Williams punch somebody out of the way of a lightning bolt. Specifically within a millionth of a second. As microsecond is not used, and it specifies a millionth of a second it will be hard to argue it is narrative hyperbole or the writer not knowing what a microsecond is.
Taken from The Final Crusade.
Chiun is able to move faster than the electricital signal in a wire. After a detonator was used by accident. Chiun explains in detail how he was actually moving faster than the electrical signal. In everyday electrical and electronic devices? Their signals on average travel 50% to 99% the speed of light as electromagnetic waves.
Now moving to radiation, and light.
Taken from Ground Zero.
Remo Williams can run circles around neutrons from a neutron bomb after it went off, and maintains a safe distance from the expanding radiation field. For reference neutrons move in the realm of 20,000 kilometers per second at bare minimum for a rating of MeV 2. From a neutron bomb they would actually be a lot faster than that. Since they are close to 14 MeV. Which means they're more along the lines of moving at 50,000 kilometers per second. Remo can comfortably keep out of their reach when they're shooting towards him.