Applying for spousal visa extension

[FashionPoke]

Hi all,
Hoping you can help me in clarifying the following questions please:
My husband's visa expires on the 8th of June 2017. I was told I need to apply at least 28days before the visa expires, as this will reduce the likelihood of overlapping using the 5 years route;
Question 1: Will it be ok to apply around the end of May? I was thinking to post the application form around the 25th of May 2017. 2 weeks before his visa expires. Will this be ok or will it impact us? My reason is delaying is because, this will be after pay day. We'll have enough money for the application form, as I just realised the fees have been increased to £996. Also were having to delay because apparently to go through the NARIC route of obtaining English requirement we need a letter from his University saying he studied in English. This is a very long process and will require for him to travel back home. So he's having to do the English CEFR A2 test. We need to book this ASAP.

Question 2: Does anyone know how much the CEFR A2 English test cost? and what it will entail?

Question 3: Do we need a letter from the Estate agent we are renting from? Or will our tenancy agreement be enough? We rent a 2 bedroom house. Just myself, my husband and our son (British born) (under 1 year old). We communicate with the estate agent and not directly to the landlord. Do we need a letter from the Agent or the landlord?

Question 4: Does my husband need to include his employment and earnings? I earn over 20k so I earn more than the financial requirement. I also have a part time job that is separate. Do I need to include both jobs and my husband's? or is it ok to just include one of my job( the one I earn 20k)?

Question 5: The first time we applied, I sent in several letters from my employer, and my letter of invitation, my husband also sent in a letter with his application stating his intent to apply. Do we need to include any letter for this extension? if so, what letters should we include?

Question 6: We will be applying using the online route, because I feel it'll make the application a lot tidier and easy for them to read. But there was a section asking about my husband's involvement with my son and his role in bringing him up and why he cant go back to his own country, what family members he has in his own country.
This questions were quite worrying because I am not sure how we should answer this. Firstly, my husband looks after my son during the day he works at nights and I work in the day time. So my son is very much used to him. He also has his parents and siblings in his home country but they have their own family and responsibilities. Not conducive for our family to join them. So I'm not sure how to answer this question? Any ideas?

I appreciate that I've asked a lot of question. But please help me. I'm running out of time. Thanks in advance.