1. She has requested a "brand name plasticware company that do "parties" at your house" kitchen tea. This means that if people purchase items the benefits of the profits will go to my sister. I have a feeling people may feel pressured to purchase items to give to her as well. - How do I tell her that I think this is tacky?
What is a "kitchen tea"? Is that the same as a bridal shower? If so, yes, that is usually how these things work, the guests purchase items for the bride. I don't particularly care for it, either, but unless you are in charge of it, I don't think your opinion matters. If you are hosting, I think you can tell her you don't feel comfortable with it, but I think you should find some other word than "tacky."
2. If the church is 15 minutes from your house, why can't you go get ready at your sisters place and then make sure you give yourself time to go home and pick up your husband and sons? This is your sister's wedding and you are a bridesmaid. Did she do those things for you or your other sister? Sometimes you do things that aren't convenient for you, because, well, it's not always about you. If cost isn't an issue (and you say it is not, as long as it doesn't inconvenience you), then I think you should plan to be there with the rest of the bridal party.
3. Is your sister the one who wants the 3 separate parts to the night? If so, take her at her word, and go to the part that you are comfortable with. I'd think accepting the honor of being a bridesmaid sort of implies that you know there will be a bachelorette party / hen's night that might require you to spend a few hours away from your children. Again, did your sister go to these events for you and the other already-married sister?
4. Totally none of your business. Ignore her. She'll figure it out and I doubt she wants your advice.
The overall tone I get from your post is that your sister's wedding is a burden on you. My advice is to remember she is your sister, and this is her wedding. Unless she was a total bat at your wedding, I don't see why these are "small bridezilla" issues to you.