Indeed, both DMT5 and DTrader charts use the same data feed, but there is one main difference between them:
DMT5 chart: Displays the spread which is the difference between the bid and ask prices
DTrader chart: Displays the mid-price (the average of the bid and ask prices).
Because of this, you’ll see a similar price movement on both charts, but the actual price differs between spread and mid-price.
As for the historical data on the Webtrader platform. You can only obtain the data in ticks for 1 hour. However, you can generate 1-day interval data which you will be able to see the daily Open,High,Low, and Close price.