Hey,
It's clear that you've put a fair bit of work into this, so first of all I want to say good job on doing that & also getting on top of your PSMT early.
If you haven't already I'm going to recommend you read this
high level PSMT example by QCAA. Note that the language is relatively simple and straight forward. Often our instinct for school work is to true and "sound smart" but here your goal for your writing shouldn't be to try and sound smart - focus on being clear, concise & easily understood. Part of this is about cutting your sentences down into shorter and simpler ones; another aspect is making sure you follow grammar conventions. Additionally, I think your structure and sequencing could use a bit of work to ensure the report is clear and flows smoothly with logical ordering.
Throughout your report it's written like you're writing it for a school task and your explanations and justifications reflect that. That makes sense since it
is a school task but try to approach it pretending it isn't for school.
If you only edit one section of your PSMT make it your discussion. There are points that I know you've thought of from your writing earlier in the report that should be in the discussion and isn't making its way there. I advise you reconsider your approach to "reasonable" "acceptable" and "valid". Consider questions like: will they actually be able to save that much each week? Does the cost of the holiday make sense? Is it likely to actually cost more? less? why? Is the length of time spent saving for the holiday appropriate? What influences the accuracy of your predictions?
Best of luck, I hope this helps and please feel free to reply with any questions or comments!