Sorry to hear about your rejection… I’m sure there was a lot of effort put into your project but it’s good to see that you haven’t given up since you are asking for advice here. Perseverance is key to success!
Now, let’s get to what we came up with after checking out your theme. Please keep in mind, these are our subjective thoughts, the reviewer might have different opinions:
There’s no such thing as too much testing. It’s very important to test your project on every device and platform OS you can get your hands on. Testing on real world devices is key to success. On the device I’m using now (13’’ laptop) I notice there’s one or more items that cause a horizontal overflow. Also, you need to clear your floats, for example the main nav is not cleared.
Design weights a lot. There are lots of issues with typography, text hierarchies, at least on the front page. You also need to use higher quality icons - see search icon from main navbar. There are lots of options out there, font awesome would be a suggestion. Also, the text in the slider is not vertically aligned to its’ dark container. Items here should also be proportionally displaced.
Code is very important. We can’t see your code but you really have to ensure it’s up to ThemeForest standards. Ensure that you use ThemeCheck, naming conventions, in general ensure that all items mentioned in the ThemeForest guidelines and requirements are checked. Some issues that we can spot are that the e-mail is present in the footer, which, at least if it belongs to the admin it surely is frowned upon, and also that the links in your navigation bar do not work at all. For example, we couldn’t check if the main WordPress feature - blogging - is actually implemented by your theme.
To conclude, it’s probably best that you study free and paid themes thoroughly to see how things are done and then come up with a new theme.