Comma, Present-Partciple, and Also

Dear teachers,

I read an article as seen in the below and would like to have your feedback regarding the 4 points in the below:

Last September we forecast that the economy would grow 2.2% in 2017, meaning the outlook has worsened since then. The Korean economy grew 2.6% in 2015, and about 2.5% in 2016. The growth rate is expected to contract further in 2017. We forecast that the growth rate will shrink first because of the major internal and external uncertainties. Another factor is that the country lacks policies that can prop up the economy
when it is weak. Considering the fiscal sustainability problems, the country’s ability to enforce proactive financial policies has decreased, leading us to forecast a contracted growth.
The Organization for Economic Cooperation and Development (OECD) also lowered its growth projection for the country from 3% to 2.6%, adding to the alarm.

(1) Comma
Regarding the first sentence, should we put "comma" after "Last September"?

Last September, we forecast that the economy would grow 2.2% in 2017, meaning the outlook has worsened since then.

My understanding is that we should put "comma" when adverb or adverbial clause (or phrase) is put before a sentence. Is this correct?

(2) meaning
Last September, we forecast that the economy would grow 2.2% in 2017, meaning the outlook has worsened since then.

Can I re-state the above mentioned sentence as seen in the below?
=> Last September, we forecast that the economy would grow 2.2% in 2017, and we meant that the outlook has worsened since then.

(3) leading us
Considering the fiscal sustainability problems, the country’s ability to enforce proactive financial policies has decreased, leading us to forecast a contracted growth.

Can I re-state the above mentioned sentence as seen in the below?
=> Considering the fiscal sustainability problems, the country’s ability to enforce proactive financial policies has decreased, and that country's ability has led us to forecast a contracted growth.

(4) also
In the official document, can I put "also" in front of a sentence as seen in the below?
(I learned from a Korean grammar and usage book that it is not recommended to put "also" in front of a sentence in the official document.)

The Organization for Economic Cooperation and Development (OECD) also lowered its growth projection for the country from 3% to 2.6%, adding to the alarm.
=> Also, the Organization for Economic Cooperation and Development (OECD) lowered its growth projection for the country from 3% to 2.6%, adding to the alarm.

Hope to hear from you soon.

Thanks and best regards,

David Kim