Another FLR(M) timeline questions (and one about my UKC child)

I entered the UK on 3/12/14 and my visa expires on 22/07/2017. Please explain to me like a 5 year old(my brain doesn't work these days; I'm so stressed out)   :

1) 1st date and last date I can submit online application to renew my spouse visa?

2) How long after I pay IHS and fee, then submit the online application, do I have to get documents submitted?

3) Am I paying either an IHS fee or application fee for my British-born UKC daughter, who is 16 months old? I don't know why this subject is so confusing for me. I assume that since she is a UKC, the answer is no, but I need to be 100% clear on these things.

I apologise for asking old questions but my marriage has been rocky and I did not know until recently if I was going to apply or just separate from my husband and return to the US.
This has left me depressed and anxious, unable to even think about the application process until a few days ago. I can gather all the documents needed by the end of this week. 

I'm so sorry to hear about your relationship with your husband.

1) The earliest you can apply is 28 days before the 30 month mark that you've been in the UK.

So you entered on 3/12/14, which means 30 months from then is 3/6/17. 28 days before that is 6/5/17 which is the earliest you can apply. You have to apply before your visa expiry date so...

Earliest you can apply: now
Latest you can apply: 22/7/17

2) I just missed the electronic submission system so I can't answer sorry.

3) No. Your daughter should be classed as 100% British in this. She is not involved in the visa process. Therefore she doesn't need to pay IHS and she is not included in the minimum financial requirements. She merely needs mentioning in your application as your child

2- You can still use the paper FLR(M) form. We are recommending that people do this because the online system can be glitchy and we are unable to see it so can't help as easily with any questions that you may have.