"Also in theory, if a player has a specific play pattern (for example: under 2x), you could generate outcomes that make the player lose"
( the outcome of the dice is predefined before you go to the next bet or set the new bet amounts, so the system won't be able to know if for example you stop and go all in for the next bet as the roll has been already determined ),
Yes, so the idea is that if I bet "under 50" all the time, you will keep making a result higher than 50. Of course if you do this in such a clear way, the player could abuse this by betting above 50 with a bigger bet. So I do not think you are doing this, but it is a potential flaw in your system. Other provably fair mechanisms don't have this flaw.
the jackpot is purely random as you can see people that dind't played the minimum amount already won some but didn't credited because of it.
Sure thing... but we, the players, cannot prove that. Ideally the jackpot is calculated in a provably fair way. Still shared jackpots/bonuses almost never can be properly provably fair because the site can fake to be a winner.. but still some clear public calculation is better than "just random".
.. as i saw on other website some people still acuse websites of cheating.
Some people will always complain. But this is about being really provably fair. So you can ensure that the player can verify their bets and know that the result was generated in a way that the site couldn't influence the outcome. Currently the site can influence the outcome (eg make sure no one wins the jackpot ever or try to predict next rolls based on betting patterns.)
edit: to be clear. I do not think you are cheating the players at all
I am just giving feedback and think you should improve your provably fair implementation to be better and IMO if you want to call it provably fair at all. GL with your site