Multi-step assessment tool — front-end form build with webhook integration

I'm building a lead generation assessment tool for my existing recruitment website. Respondents answer 15 questions across 5 dimensions , see their results visualised as bell curve charts, then hit a gate form before accessing their full report.

Pages and Bell curve logic is already designed.

What I need built:

Multi-step question flow (15 questions, 5 sections, progress indicator)
Scoring logic (I'll provide the formula) calculated client-side
Six bell curve visualisations displayed after completion, before the gate
Gate form capturing: first name, last name, email, phone, LinkedIn URL
On submission: POST all scores + contact details as JSON to a Make.com webhook (I provide the URL)
Simple thank-you/confirmation page post-submit
Responsive, works on desktop and mobile

Not in scope: report generation, email delivery, CRM integration — all handled separately via existing automation.

Stack: Your choice — keep it clean and handover-friendly. Vanilla JS or lightweight framework preferred. Must integrate with an existing WordPress site.

Deliverables: Working build, webhook tested, commented code, brief doc covering how to update questions and webhook URL.

Timeline: 2 weeks preferred.

Please include examples of similar form/assessment builds with your bid.