Server not letting me join

I can't join my server, for multiple reasons. While I'm getting kicked or loading the server stops, causing me to wait, and then it does the same thing. I have a javaNULL error: connection lost or something, and that also prevents me from joining. Then the 2 times I have joined, it kicked me out immediately. I don't know why or how to fix. Here is log if that helps https://mclo.gs/jSTV15b

Thanks :D.

I also have a different problem if you are willing to answer.

My server shuts down before I can join, is there any way to keep it open for like 5 more minutes while 0 players are on so my laptop can actually load the mods?

(I've already set the slots to two players, as just me and my friend play, and it still doesn't load.)