Spotlight doesn't show applications
I am not sure whether you have tried this step or not. 

Open Terminal window from LaunchPad. 

First, turn off Spotlight:

sudo mdutil -a -i off 


Next, unload the metadata file that controls Spotlight’s index:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist 


Use the following command to re-loads the index :

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist'''


As a last step, turn Spotlight back on:

sudo mdutil -a -i on 


After a few minutes to rebuild the index, Spotlight should be functioning as normal.

Let me know how it goes. 

Update: I have a script for it and it is helping me in such kinds of issue. 

#!/bin/bash
# This script is designed to fix Spotlight indexing issues
# by removing the existing Spotlight index and forcing Spotlight
# to create a new search index.

# Turn Spotlight indexing off

/usr/bin/mdutil -i off /

# Delete the Spotlight folder on the root level of the boot volume

/bin/rm -rf /.Spotlight*

# Turn Spotlight indexing on

/usr/bin/mdutil -i on /

# Force Spotlight re-indexing on the boot volume

/usr/bin/mdutil -E /


Save this as .sh and run from the terminal. It should help you to fix your issue too.