Judging by your goals you want to improve your muscular endurance and to some degree strength. Your goals for 100 push ups means you need to be doing more. For example, you are doing one set of 27/28 reps is this your max? If so then break it down and do several sets of sub max, this could mean doing 3 or 4 sets of 20 push ups. Also mix it up and do different styles like diamond, wide, close, elevated etc. This will help work different muscles more and improving your overall upper body strength.
Just my advice, other than that carry on!
I will persist until I succeed.