I'll chuck in here and say yes psych is alot more memorisation- that said you also need to understand and apply the theory to be able to do well in scenario based questions in section b for the exam.
As for chem and its calculations, yes its not everyone but I will say from year 11 to year 12 you don't learn new concepts (except for the universal gas equation) its more building on the content covered in 1/2
I will i don't think you will struggle to do psych 3/4 without 1/2 ik many people who have done it and scored very well, but since you like chem I do believe you should give it a good hot go.
I encourage you to try reading a little ahead in janruary not too much (maybe even attending a headstart lecture) and try to get exposed to the content early and complete some past exam questions (that are unit 3 calculation based) and see how that goes.
Getting a tutor is also an option, for a subject you enjoy you will work hard so you can use a tutor as an additional resource.
There is also plenty of free resources such as khan academy that can be very helpful.
But more importantly, if you do decide to drop chem, psych 3/4 will treat you will the way to study for psych is
1. Make detailed study notes, that summarise the information and cover all the study design points
2. Make flashcards (or some other resource) and memorise the content
- but don't memorise terms and definitions, memorise a structure to your response
(e.g. when memorising the steps of the spinal reflex, you should memorise in a way the can be applied to a scenario; for instance when you touch a handle of a hot pan)
3. Complete practice questions and get feedback (examiner reports can also be helpful for this as well)
~colline has provided some points so please do pay attention to was she has said
All the best
T&S