Making a choropleth in D3 by intersecting a MultiPolygon and a Point GeoJSON

Question

I am trying to generate a choropleth map showing crimes per neighborhoods: I have a layer showing the neighborhood boundaries of the city of San Francisco, and point data showing incidences of crime for 2018. My first objective is to group and sum the number of crimes per neighborhoods, where the points and neighborhood polygon intersect respectively.

My second objective is to normalize the dataset by dividing the number of crimes per population within a neighborhood (for the latter I suppose I could use U.S. census block data).

Here's my html and JS code in JSFiddle for reference. I'm pulling both of my GeoJSON from my local directory via endpoints on a separate python file:

###########################
# Dependencies
###########################
#Set up Flask (Server)
from flask import (
    Flask,
    render_template,
    jsonify,
    request,
    redirect,
    url_for)

#SQL Alchemy
import sqlalchemy
from sqlalchemy.ext.automap import automap_base
from sqlalchemy.orm import Session
from sqlalchemy import create_engine, func, desc, select
from flask_sqlalchemy import SQLAlchemy


import pandas as pd, json
import numpy as np
import os

###########################
# Convert Json to GeoJson
###########################
def df_to_geojson(df, properties, lat='Y', lon='X'):

# create a new python dict to contain our geojson data, using geojson format
    geojson = {'type':'FeatureCollection', 'features':[]}

    # loop through each row in the dataframe and convert each row to geojson format
    for _, row in df.iterrows():
        # create a feature template to fill in
        feature = {'type':'Feature',
                'properties':{},
                'geometry':{'type':'Point',
                            'coordinates':[]}}

        # fill in the coordinates
        feature['geometry']['coordinates'] = [row[lon],row[lat]]

        # for each column, get the value and add it as a new feature property
        for prop in properties:
            feature['properties'][prop] = row[prop]

        # add this feature (aka, converted dataframe row) to the list of features inside our dict
        geojson['features'].append(feature)

    return geojson


###########################
# Flask Setup
###########################
#create the engine with sqlite
app = Flask(__name__)

#app.config['SQLALCHEMY_DATABASE_URI'] = os.environ.get('DATABASE_URL', '') or "sqlite:///db/crimedata2017.sqlite"

engine = create_engine("sqlite:///db/crimedata.sqlite")

# reflect an existing database into a new model
Base = automap_base()

# reflect the tables
Base.prepare(engine, reflect=True)

Crime2018 = Base.classes.crimedata2018

#################################################
# Database Setup
#################################################

#db = SQLAlchemy(app)
session = Session(engine)

# create route that renders index.html template
@app.route("/")
def home():
    return render_template("index.html")

@app.route("/api/crimedata/sfgrid")
def sfgrid():
    json_data = os.path.join(app.static_folder, 'sfneighborhoods.geojson')
    with open(json_data) as blog_file:
        data = json.load(blog_file)
        return jsonify(data)


@app.route("/api/crimedata/2018/theft")
def crimedata2018theft():

    #Grab all the columns we need and create a list
    sel2018 = [Crime2018.IncidntNum,
        Crime2018.Category,
        Crime2018.Descript,
        Crime2018.DayOfWeek,
        Crime2018.Date,
        Crime2018.Time,
        Crime2018.PdDistrict,
        Crime2018.Resolution,
        Crime2018.Address,
        Crime2018.X,
        Crime2018.Y]    

    results2018 = session.query(*sel2018).\
        filter(Crime2018.Category == "LARCENY/THEFT").all()

    #Store results into a dataframe
    df = pd.DataFrame(results2018, columns=['IncidntNum','Category','Descript',
                                        'DayOfWeek', 'Date', 'Time', 'PdDistrict',
                                        'Resolution', 'Address', 'X', 'Y'])


    # useful_columns  = ['IncidntNum','Category','Descript',
    #                                 'DayOfWeek', 'Date', 'Time', 'PdDistrict',
    #                                 'Resolution', 'Address', 'X', 'Y']

    # geojson_dict = df_to_geojson(df, properties=useful_columns)

    #Return the dataframe in json format
    return jsonify(df.to_dict(orient="records"))    


##Assault End Point    
@app.route("/api/crimedata/2018/assault")
def crimedata2018assault():

    #Grab all the columns we need and create a list
    sel2018 = [Crime2018.IncidntNum,
        Crime2018.Category,
        Crime2018.Descript,
        Crime2018.DayOfWeek,
        Crime2018.Date,
        Crime2018.Time,
        Crime2018.PdDistrict,
        Crime2018.Resolution,
        Crime2018.Address,
        Crime2018.X,
        Crime2018.Y]    

    results2018 = session.query(*sel2018).\
        filter(Crime2018.Category == "ASSAULT").all()

    #Store results into a dataframe
    df = pd.DataFrame(results2018, columns=['IncidntNum','Category','Descript',
                                        'DayOfWeek', 'Date', 'Time', 'PdDistrict',
                                        'Resolution', 'Address', 'X', 'Y'])


    # useful_columns  = ['IncidntNum','Category','Descript',
    #                                 'DayOfWeek', 'Date', 'Time', 'PdDistrict',
    #                                 'Resolution', 'Address', 'X', 'Y']

    # geojson_dict = df_to_geojson(df, properties=useful_columns)

    #Return the dataframe in json format
    return jsonify(df.to_dict(orient="records"))    

if __name__ == "__main__":
    app.run(debug=True)