Thats great, you are gaining a TON of really valuable experience. It also means that you are worth a hell of out lot more to this company than 23k. If you were to quit and they had to hire somebody to fill this role, they would have a very hard time finding somebody to do all that at 23k, even at 35k it would be difficult. Junior developers are not really expected to be able to do everything that you're doing right now.

If I were I would start applying to jobs, and when they ask you what salary you would expect I would go for 35k, you could reasonably push it to 40k depending on how confident you are at negotiating.

Feel free to PM me if you have anymore questions.