Sending in visa app.

Ok, I am going to apply for the visitor visa for two years...I was told by immigration they COULD deny me entry but were instead giving me limited entry for 1 month...

I want to send a letter in with my application, I will have one from my so stating he intends to sponsor me and documents to show he can, that he has permission from the landlords (his parents happen to rent houses, and he and I found it on a website while in the US, not knowing it was one of his parents!! ). I will also enclose a letter from my ex stating that I do have permission to have my son in the UK.

Should I enclose a copy of the divorce papers which wont be final but will have been filed? And as for my letter, should I tell them I have been to the UK but was given limited entry? Will just letting them know to begin with help? We're going for the visa because of that and also because we dont want any red flags raised because of the length/frequency of the trips...

I know there was more I wanted to ask but I cant remember

Oh..has my passport been flagged in some way? It was stamped that I had leave to remain or whatever until the 7th of Dec, I left on the 5th. Would telling them that in the letter help, since I left as I was instructed, and I left a bit early?

I'm sorry so many questions I am just so worried

A bit more on my passport...when they stamped it they stamped it with the one that says leave to enter for/until ________ no work or recourse to public funds. the for was crossed out and then the date I could stay until was put in...so what exactly was that? It has 3 letters and 2 numbers on the top line, do they mean something?

The immigration officer said to get a visitor or fiancee visa, since we're not ready for fiancee visa, that they recommended a visitor one or the fiancee and I am going for visitor wont count against me will it?

Visitor visas are only valid for 6 months.  Where did you hear you could get one for 2 years? 

theres 6 months 2 years 5 and I believe 10 years. I went to ukvisas.gov.uk

As an American, you don't qualify for the 2 year visitor's visa.  You were told to get a visitor's visa by the IO because you were denied entry and given a month to leave.  Your best bet is to get a fiancee visa because if you apply for a visitor's visa, you'll be given 6 months and that's it.  If you explain why you're coming to the UK, that you basically have your ex's permission to take your kid, etc, it will look like you're coming to settle.  And that's the fastest way to a denial for any visa.