I think we have very little disagreement about the fundamentals here. It sounds to me like you have done some "experimenting on the word" in your search for fundamental truths that lead to happiness, and you have found some that have borne good fruit. I think that if you continue to honestly search for truth, and doing good for the sake of doing good, then you will be just fine in the afterlife.
I've gone through quite a few periods in my life when I've honestly wondered, "What if it's all a lie? What if there is no afterlife, or my church has it all wrong?" Being of a logical and scientific turn of mind, I then said, "OK, take the hypothesis that there is no afterlife, what would you do differently her and now?" I asked myself if I'd wear different clothes, date different people. Would I eat differently? Smoke cigarettes? Get drunk every evening like my next door neighbors do? Steal? Have sex outside of marriage?
I looked at even the most glamorous representations of many of these behaviors, and found that they didn't look like they led to happiness. The drunken parties my neighbors throw every night don't even look like they're fun before they often turn into screaming matches, and most of the people who hang out there don't seem to have stable jobs, homes, families, or even relationships.
I also saw that being a member of the Church gave me a safety net for many of the areas that I'd fall down in my life alone. I know that I'll have a whole crowd of people happy to meet me and be my new friends when I move someplace new (it's still hard for me to socialize, but at least I have a starting place). There are opportunities to serve others, learn from people who've been through my stage of life and beyond, and share my own talents. I don't have to worry that my donations to humanitarian causes are being spent on executives with huge salaries and expensive infomercials. The list goes on and on.
Then I considered that if in every area I could reasonably test in this life, living the gospel made me happier than not, then there might also be truth in the places I couldn't test -- and even if there's not, it really isn't that hard for me to do the little extras. That's what makes it worth it for me. I have had spiritual experiences, but they are somehow easy to dismiss or forget in the tough times. during those times, my logic keeps me on the straight and narrow until I can feel His hand in my life again (and I always have felt Him again).
As for a loving God creating us then waiting to punish us, I don't think that's how it works at all. I have an 18 month old daughter, and I love her and want the best for her. I make rules about what she can eat (not too many sweets), and when she has to sleep, and what she can play with (she's not allowed to dance with my sharp scissors). There are times when she gets into something I don't want her to, and she gets upset when I take it away. When she gets older, I'll make rules based on my greater experience, and if she deliberately breaks them, there will be consequences for her actions. I may have to punish her for small (in the grand scheme of things) disobediences in order to keep her from heading down a path that I know will lead to unhappiness (for instance, I don't think that drug use or teen sex can ever be a recipe for happiness, so I'll do my best to make sure she has good friends and stays out of dangerous situations). I will never be so angry at her that I'll stop loving her, even if she makes some decisions that disappoint me or make me sad. I know that school and college will be difficult at times, but I'll send her anyway, because I know that she can't grow up to be a competent adult if I lock her in the house all the time. I could be said to be her creator -- almost every bit of her physical body was once a part of me, but there was something eternal -- some personality -- that I just made a home for.
I think that this is exactly the way God feels about us, only his love and experience are infinitely greater than ours. I believe that he created our spirits (and also the world we live on and therefore our bodies), but that He had some kind of material to start from -- some part of our personality that is eternal even beyond God. He sent us to earth to gain the experience we'd need to become all that we can be in the eternities -- and I believe that we will be working, progressing, and creating in the afterlife. He knew that it would be hard, and that not all of us would live up to our full potential, but He also knew that if we didn't experience mortality, none of us could progress much further than we had already. I believe that He wants to do everything in His power to help us succeed. I believe the only real "punishment" in store is having to look in His loving face and see the sad look of disappointment there. I believe that it will be so painful to those who willfully rebelled that they won't want to be near Him, and so will not be able to dwell in His presence, and the eternal soul wrenching guilt of knowing what you could have been if you'd only done as He asked. I believe that anyone who sincerely wants to do good and be the best they can be, will have an opportunity to do so either in this life or the next. I believe that the better we can become in this life, the easier it will be to keep moving forward in the next, but that He'll give us all the chances we need as long as we're sincerely doing the best with what we have (As for what "Sincerely doing you best" entails -- only God can judge that).
As for happiness versus cheap thrills, think of a drug addict. He gets cheap thrills, but very little real happiness as he destroys his relationships, his health, his career, and ultimately his whole life in search of more drugs. If your faith in God leads you to a religion that teaches you not to waste your time, money, etc on addictive substances, then following that religion will keep you from doing things that will certainly make you unhappy, and encourage you to do things that will make you happy, even if they're not all as obvious as not doing drugs.
