I've got 3 stucked transactions that don't seem to go through even after waiting more than a week.
In the end I don't really care if they reach their destination, I'd even prefer to cancel the transactions.
How can I withdraw the transactions? I want the network to abandon them but I don't know how.
Well if you actually want them to be canceled you just need to way, and the network could eventually drop them, and the coins will gt back to your account. This actually made a lot of money to a friend of mine. He was going to sell 0.07 bitcoins to neteller, but he used low fees. The transaction was never completed and he eventually got the same amount of bitcoins back in his wallet. When he got them back, bitcoin was already at $3500. He realized how lucky he was, so he kept them, and eventually sold them close to the top. I keep telling him that he should buy them back now, after the dip, but he is still not convinced.
Anyway, like I said, you can just wait, and if the fees are that low, they will be rejected eventually.
There is another option to push your transaction, that I've never tried. It's called the Child Pays for Parent (CPFP). From what I've read, usually transactions send the coins to the receiver, and a "change" back to you. You can usually spend that change, even if the tx is not confirmed yet, so you can send the change back to you, and this time by including a fee that is big enough for the tx to confirm. This way, miners will increase the priority on both the transactions and they will complete at the same time.
Like I said I've never done this, and I will leave you this link, where I've got the information:
https://bitcoinmagazine.com/articles/what-to-do-if-your-bitcoin-transaction-gets-stuck-1481042383/
You can also try to use a transaction accelerator. The site mentions ViaBTC.