Homosexuality and abortion are scarcely mentioned in the Bible at all.
First, let’s look at your scriptural references regarding homosexuality:
Genesis 18 — there is absolutely no mention of homosexuality anywhere in this chapter.
Genesis 19:4–11 — This has to do with rape, as the men of Sodom attempted to rape Lot’s angel guests. Not homosexuality. I think we can all agree that rape of any kind is a sin, can’t we?
Isaiah 3:9 — this one says, “they parade their sin like Sodom; they do not hide it.” To understand this one, you must understand what the sin of Sodom really was. To do this, you need to look at what the prophet Ezekiel had to say on the subject — “Now this was the sin of your sister Sodom: She and her daughters were arrogant, overfed and unconcerned; they did not help the poor and needy.” (Ezekiel 16:49). Note there’s no mention of homosexuality anywhere in that list of sins. Greed, arrogance, failure to take care of the needy, inhospitality (which would include the way the men of the town treated Lot’s angel guests), etc. But not homosexuality.
Jude 1:7 — in the KJV translation, the reference is to “strange flesh”. This refers to the men of Sodom raping angels. Sex between humans and angels was forbidden (and attempted rape, which is what went on with the angels in Sodom, is forbidden under any circumstances).
Romans 1:27 — I’m always fascinated that people who use the first chapter of Romans boil it down to this one verse, completely missing the context. These were not homosexual people. These were heterosexual people. Same sex attractions were a punishment from God, not the sin. So what was the sin? You have to read verses 1:21–25. The sins were failure to glorify God, failure to thank God, and idol worship. The punishment is described in verse 1:26. Yes, God caused these people to have same sex attractions. And back in those days, before IV fertilization and artificial insemination, that was a very effective way of causing an entire people to die out — by removing their ability to procreate. But no — just because God meted that out as a punishment doesn’t indicate that it’s a sin.
OK — that pretty much destroys your argument that homosexuality is one of the “biggest sins” in scripture.
Now, let’s look at what you have against abortion. Oh, look! Only one passage! In Proverbs 6:16–19, there’s a list of seven things that God finds “detestable”, and one of them is “hands that shed innocent blood”. But there’s nothing that extends this to an embryo. According to the census rules outlined in the book of Numbers, babies didn’t even count until they were a month old. Proverbs 6:17 did indeed condemn the murder of the innocent, but that referred to those already born. If every zygote and every embryo counted as a full-fledged person, why would God Himself kill so many of them? Less than half of all fertilized eggs ever turn into fully gestated babies. Want more? Here are some bible passages that mention abortion (as well as infanticide), but I don’t think you’re going to like what they say, as abortion isn’t generally condemned.
And ask yourself this — if homosexuality and abortion are the “biggest sins” in the Bible, wouldn’t they be mentioned more often? There are a ton of sins mentioned far more often — idolatry, failure to take care of the needy, greed, injustice, hatred, and many others. Worth pointing out — Jesus Christ Himself didn’t say a word about either homosexuality or abortion.
You’re just one of many who has fallen into the trap of using the Bible to justify your own personal bigotries. Which is also a sin, and one that you’ll have to answer for someday.