Hi @Phoe,
Ok well done! So we can start from here!
Before answering, can I ask you if you can open a new thread? Please because this question is now out of topic!
Now, to answer your question. A topic of interest may be the following:
So you can have the general idea on what to do. I do think that the trimming option you propose are very permissive, and I usually go stricter (such as -p-trunc-len-f 245; -p-trunc-len-r 180). However, given that the quality of your reverse read drop so early, you would loose the overlapping region completely (please note dada2 requires at least 12 bp of overlap). So you may start with your parameters and see how many sequence you get at the end of the dada2 process. Then try more stringent settings. This try and repeat is very normal with this type of analysis so I would not expect to get it right at first try!
In worst case, you may savage your data by using forward read only (and dada2 single as well!)
Hope it helps
Luca