I agree with all of this. Firstly, as Catholics, we believe that salvation is only through Jesus Christ, and also that there will be non-Catholics and non-Christians in Heaven, all saved by Christ. The Church regards as Christian all those who have faith in the Father, Son, and Holy Spirit, the same beliefs in them as defined (not invented) at Nicaea, Ephesus, etc. Hence why if you convert and were already baptized in a church that shares this belief, you won’t have to be baptized again. Obviously others are “Christian” in another sense, believing in and worshipping Jesus Christ as savior. The Church uses the former definition however in defining its baptismal and ecumenical relationships with other churches.
And from your signature, it looks like you have read the Bible and prayed, etc. Keep doing all of that. You need to look into Christian doctrinal history and compare it with what you have read in the Bible and what you know about Catholicism, Orthodoxy, the various Protesant churches, etc. We all can’t be right, even if we may all share certain beliefs. So, compare what you find to the Bible. Look to what the early Christians believed from the writings that we have. Look at the arguments for each church you are investigating, and do the same comparisons.
It may help if you let us know specifically what you are having difficulty with!