A 595 on the official mock is a solid, honest baseline to build from, and a 100-point jump to 695 is a realistic target with the right approach. The thing to be clear-eyed about up front is the timeline. A gain of that size usually comes from real mastery built topic by topic, and that generally takes time, so I would let the prep determine the test date rather than locking in a date first and trying to cram the score gain into it.
It is also worth keeping the baseline in perspective. A single mock tells you the size of the gap between where you are and where you want to be, which is useful for setting expectations. But it does not give you a topic-level diagnosis of what is actually weak. That picture comes from the studying itself, not from the mock.
Here is the approach that tends to move a score 100 points. Study one topic at a time. Take a single area (rates, then number properties, then a Verbal question type like Assumptions, and so on), learn the concepts, formulas, and techniques thoroughly, and then practice only that topic until your accuracy is consistently high before moving on. Do not worry about timing early. Build accuracy first. When the approach to a question type becomes automatic, the speed tends to follow on its own.
The part most people skip is error analysis, and it is usually where the improvement actually happens. For every question you miss, figure out what went wrong. Was it a concept you did not know, a misread, a careless error, or a trap answer you fell for? Then redo the question from scratch later to confirm the fix held. That review loop is what turns practice into a higher score.
A clear, comprehensive, structured prep course can help a lot here, because it sequences the topics in the right order, isolates them one at a time, and tracks your accuracy by topic and difficulty so you can see exactly where the gaps are closing and where they are not. A 100-point jump generally comes from that kind of organized, depth-first work rather than loose question drilling.
On the timeline itself: once you have worked through the content and your topic-level accuracy is strong, start taking full-length practice tests to confirm the score holds up under real conditions. If your mocks are landing around your target as your date approaches, you are ready. If they are not, pushing the date usually gives you a better outcome than going in undercooked.
Good luck!
Scott