I don't know if th intention was to make Neelix a comedy character and if they realized that it was leading nowhere and therefore decided to add some tragic events to his backstory or if they had that in mind already from the beginning.
Whatever it was, I'm glad that they did what they did because they actually managed to create a very interesting character.
In the first episodes, Neelix appears to be a merry, good-humored guy, however a bit annoying and over-reacting character.
All that changes in "Jetrel". Then we find out about the tragic events in Neelix's life and all of a sudden it turns out that the poor guy have some serious issues as a result of what happened to his family.
Neelix's whole world and whole life was shattered when his family was killed during the Haakonian attack on Rinax. He basically went nuts after that. he even became a drug addict for a while (due to the book "Pathways" by Jeri Taylor) and was helped out of the addiction by his friend Wixiban.
After Wixiban was arrested by the Ubeans, Neelix was on his own. He found his way back to the area near Talax and started to trade with the kazon sects among others. Then he ended up on Ocampa, traded with jabin, fell in love with Kes, had to run away from the Kazon-Ogla after stealing water to give Kes, ran into the Voyagers which helped him to rescue Kes and finally decided to stay on Voyager which Janeway accepted.
However, he still had his demons inside. Despite his exaggerated cheerfulness and bragging about knowing everything about the part of space they were in, he must have realized deep inside that he had became a very tiny fish in a very big pond on board Voyager. Therefore he did everything he could to prove his importance for the crew. He just had to be the star of the show in all possible ways so he became the food and supply expert, started to cook food and constantly came up with whims like being "Morale Officer" and later on a journalist.
All that was probably triggered by the fact that he was very unsecure. His jealousy over Kes was a result of this. When he saw that kes had adapted much better tothe life on Voyager than he had, he became paranoid that he would lose her to Paris or some other Starfleet Officer and finally it happened that he lost Kes because of his jealousy and over-protecting ways.
Even his constant efforts to make people happy in so many ways was a result of his unnsecurity and the tragic events in his life. He kept himself happy and the demons away by trying to cheer up everyone else on the ship.
His attitude to Tuvok is typical for that. He must have felt that Tuvok wasn't particularily fond of him and he just couldn't understand and realize that Tuvok as a Vulcan kept his emotions under strong control. More that that, he couldn't stand the fact that Tuvok didn't respond the way he wanted to his efforts to cheer everyone up. Therefore he kept pestering Tuvok with all the whims he could come up with.
But all tat is what makes Neelix such a good character! in fact, due to his terrible and tragic background , he was actually normal. He acted just like many people would do if they had such horrible memories to live with. In that way he was a very realistic character.
As for his interactions with Tuvok, they were always great to watch just because they were so different, really two opposites if any.