As a former SEAS applicant with a 45 study score in English, I think I can lend a hand here.
Basically, applying for SEAS will not adjust your results in any particular subject, nor will it adjust your final ATAR result. However, what a SEAS application will do is if your score is around the cutoff point for your desired university degree, then the tertiary institution will give you a little bit more consideration and take into account that if personal circumstances had been better during year 12, then you may probably have achieved the required score.
For example, say you need a study score of 35 in English and you get 34 - they may be a tad more lenient. Or alternatively, you need an ATAR of 83 and you only get 79 - again they may be more lenient in their selection.
As for your actual English SACs, I got around the same marks as you did during Unit 3. Based on my (somewhat) poor maths skills it seems that based on your text response, context and oral you are sitting on a collective 67/80. Based on what I got on text, context and oral I was sitting on 70/80, and I went on to get your desired score, a 45. So not a huge difference, especially due to the fact that they are just SACs and not an exam.
So without a doubt give the SEAS application a crack, but just persevere with your English studies and just concentrate on the fact that the exam is SOOOO much more important than SACs (but SACs are still relatively significant at the end of the day).