This is ultimately a decision that only you and your fiancée can make.
As I understand it, you are willing to convert to Islam as a compromise. Converting on paper only, and you have set up a boundary, no circumcision, no praying 5 times per day, no ban to drinking alcohol, and you said she agrees with you. What about eating pork (Frankfurter, Wiener Schnitzel, babi guling, Spanferkel, Schweinshaxe, Schwenkbraten, bacon, as well (?). If this is also forbidden then you should avoid going to Octoberfest or Love Parade in Berlin as there will be a lot of temptation.
Now there is an additional expectation for her family that you undergo circumcision before the marriage, and that is a step break your boundary, you have set up.
If that is the case, be honest with your fiancée and remind her where your boundary is. Then the two of you can decide whether you are both comfortable moving forward together.
Ultimately, she doesn't need her parents' consent to get married. If the two of you are committed to each other and have reached a mutual understanding, you can take the next step together, even without her parent's approval. Be aware then even you marry abroad, one of you need to convert, to avoid the potential problem that your marriage can not be registered in the civil registry (dukcapil) in Indonesia.
If you break the boundary you yourself have set up then it is likely a start of slippery slope.
Also, be careful to distinguish between facts and assumptions so you don't fall into the so-called "self-bias effect."
In one post, you wrote:
'my fiancee is way younger than all her other siblings and every sibling gives them 3 juta per month as support'
But in another post, you said:
'My fiancee is the highest earner of the siblings though, she just had the best grades and made it into great SMA and uni. The rest of the family is just not poor, not rich / middle class-ish'
Those two claims appear inconsistent and don't seem to fit together, do they ?
One reason many foreigners are cautious about situations like this is that they don't want to end up in circumstances similar to that German man whose video was shared on this forum previously. That's why it's important to verify the facts and keep an objective perspective before making major life decisions.