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One thing about Audacity is that it snips sounds during playback. If you listen to the sound cloud samples on my Itch page, that is how the sounds will be in your game engine without modification. Audacity could be the cause of the abruptness you're experiencing. Since the SFX are short sounds, Audacity exaggerates the shortness by cutting off the playback quickly. In your game engine, or during playback with other software, the sounds play all the way through. I use Audacity a lot and this is something that I have noticed too.

In audacity you can add effects through the effects tab on the top (5th from the right). I personally would add silence to the end first by clicking to the end of the sound then clicking "generate" then "silence." It will prompt you with a window that will ask how much silence you want to add. Choose anything from 3 to 5 seconds. Listen to it and see if it needs reverb then. If it does, add reverb through the effects tab. The base settings are good but I would recommend adjusting them to taste. 

I personally think a better way to add effects is through your game engine. I use Godot but all modern game engines have audio effects that can be added to audio tracks. As an example, I would use an AudioEffectReverb in combination with Audio Buses in Godot to get the reverb I want on a sound. The sounds will play all the way through in your game engine as well, unlike in Audacity, so just opening the effects in your game engine might fix what you're hearing.

I hope this is helpful!

Best,

YourPalRob