The key to beating candy crush level 70 is keeping the chocolate in check. Do not let the chocolate get out until you have a good combo ready. The best combo is the sprinkle with the striped candy but if you cannot get that then you can settle for striped candy with wrapped candy combos. If you can hit 2 good combos, then you can take out the chocolate completely.
The chocolate will stay boxed in on candy crush level 70 until you let it out. Be sure to not accidentally let out the chocolate. So if you have a horizontal striped candy on the left column, be careful with it. try to drop it under the area of where you can release the chocolate.
If you have any candies you can knock out on the right, take the opportunity. Otherwise, you will mostly be working on the left column. Start from the bottom and just try and make combos. Really nothing else will beat this level, just combo it up!
If you cannot make combos then you have a bigger problem and you will not be able to beat future levels. Plan ahead and you will beat level 70 of candy crush with combos.