In regards to your questions:
5. Easier just to write one and post it... though, really, it should be your employer that writes it, not you! You can draft one though, so you know what needs to be included and can make sure your company includes everything required
6. You must include the FULL bank statement, so send all of April's statement.
If you're applying in October, you will need to send the following payslips (assuming you are paid at the end of each month):
March 2018
April 2018
May 2018
June 2018
July 2018
August 2018
September 2018
And the following bank statements:
10th Mar - 9th Apr
10th Apr - 9th May
10th May - 9th June
10th June - 9th July
10th July - 9th Aug
10th Aug - 9th Sept
10th Sept - 9th Oct
7. No, if the payslips are digital, they must be accompanied by:
"a letter from the employer on the employer’s headed paper and signed by a senior official, confirming the payslips are authentic"
This can be incorporated into the main employer letter, and it should state the amount and date of every payslip
1,2,3,4 - Awesome thanks, again just wanted to be really sure

5 - We are a pretty small company and our CEO and CFO have been supportive in giving me information and also up for signing anything required, so he won't mind if I hand to him to sign and ask to verify thats okay to do
6 - 7 - Great thank you, I have a version written up with the intension of us sending in October. I have questions beside statements, just to check those are okay?
XX/XX/2018
To The Entry Clearance Officer,
Ref: Employment confirmation - (my name)
I am writing to confirm that (my name) is currently employed at (company). as (my role). (my name) has been employed on a permanent, full-time, salaried contract with us since 01/09/2013. The total length of employment till date is 6 years. (my name) current annual salary is (££££) and they have been earning this salary since 01/06/2017.
I got a salary increase since my original contract amount, is this note here okay?
I can also confirm that the payslips and P60 provided with this application are authentic and correct, as follows:
March 2018 – Basic pre-tax salary of £, tax month 12 covering the month of March 2018.
April 2018 – Basic pre-tax salary of £, tax month 01 covering the month of April 2018.
May 2018 – Basic pre-tax salary of £, tax month 02 covering the month of May 2018.
June 2018 – Basic pre-tax salary of £, tax month 03 covering the month of June 2018.
July 2018 - Basic pre-tax salary of £2, tax month 04 covering the month of July 2018.
Note: this is in higher value due to a tiny bonus, the payslip shows this higher value, is this okay?August 2018 - Basic pre-tax salary of £, tax month 05 covering the month of August 2018.
September 2018 - Basic pre-tax salary of £, tax month 06 covering the month of September 2018.
Please Note:
The payment date on April, May, July, August and September payslips are different to the entry on the bank statements due to the clearance of funds from (company name).
The payment date on June payslip was cleared in the beginning of July 2018 due to delayed funding from investors to the company. This payment entered(my name) bank account on July 2018.
P60 – Total pre-tax income of (amount shown on P60) covering tax year to 5 April 2018.
If you require further information please contact (CEO e-mail)
Sincerely,
CEO
CEO of company Ltd.