Greetings The Pac-Man Gamer 7650.
1. The game won't harm your computer, Clickteam's executables have had the issue of being detected as malicious for some time now... sorry for the issues (Just make sure to download it from Itch.io, I haven't uploaded it on any other page).
2. In other games you would hop right online and join a lobby, however with an obscure fangame... yeah, you would need to ask someone else to play, I recently created a Discord https://discord.gg/zEAzc9mnZJ so people can get together / follow me for updates.
3. Adding a gray (Spunky) color and a brown (Tim) color should be easy, so yeah.
4. Kind of, maybe I could add stages from other games, original stages, small costumes (Like Ms. Pac-man bow or junior's hat), changing some TCP messages to UDP, I'll see.