so that I can turn back towards organised religion.
First realize that the whole point of following Jesus Christ is not to become religious, but rather to go through a complete transformation of heart through a complete demolishing of your old self. To simply accept a set of facts and theological truths is not the point of being Catholic. Thus to simply become religious without the spiritual transformation of turning away from sin and beginning the journey of uprooting everything in our heart that separates us from God-- the unforgiveness, the resentments, the pride, the impurity, the dishonesty, etc. then religion is hollow and ends up condemning one even worse, being that to those to whom much is given much is expected. The Sacraments are fountains of supernatural grace that empower us to say NO to sin and to begin our transformation. Thus to merely be Catholic and yet stay the same rotten person, is simply a recipe for hypocrisy and condemnation.
As for your questions:
"Why would God create the entire universe for the sole purpose of having people worship him?"
God commands us to worship Him because we were made for God and it is for our own good. God is to the soul what food is to the stomach and oxygen to the lungs. God is Truth, Goodness and Love itself, thus we were made for God. Some people choose to worship money, others, fame, others, the body and a life of pleasure, others choose to worship people, and all the myriad of false idols that lead to ruin by building on sand. When we worship God we are building on the rock of Christ which leads us to eternal happiness. Thus Jesus said:
“I have told you this so that my joy may be in you and that your joy may be complete.” 1John 15:11
Jesus founded His Church and gave the Church authority to teach the Truth in His name throughout the ages, despite the scoundrels and traitors that will always be among both the clergy and the laity…
"How can God send people to hell when it is actually HIM who is the one who caused them to sin?"
Hell is a built-in consequence, much like blindness is the “punishment” for plucking your own eyes out. If there is so much evil and slavery to sin in this physical world, what makes you think that there isn’t evil and slavery in the spiritual world, i.e., Satan, wicked spirits and damned souls?
SIN is the misuse of the intellect and the will. Your mind is made for Truth (GOD); your Will is made for Goodness and Love (GOD). Some people choose to not forgive, to hold on to resentments, to seek revenge, to slander and lie, to cheat and to steal, to misuse he gift of sexuality, to murder, to walk down the path of darkness rather than the path of Truth. So people condemn themselves. God calls us to seek Him. Thus Jesus said we must loge God with all our Heart, all our strength, all our soul, and all our mind; and to love neighbor as we love ourselves.
Here is a good talk which may help you understand: