How many ajax calls we can make on a custom page?

This code can almost certainly not work, at least not in the way you provided the example, so giving you advice is hard here...

1. what are your "ideas"? are they integer ids, or JSON objects or something else?

2. if so, do you process each idea separately, if so, where is the $.each() loop?

3. You send a POST request and use a URL with GET parameters...just sayin'...

4. And of course you're getting a https://httpstatuses.com/429 error like this, no properly configured server should allow something like this, otherwise every 10 year old could DoS that server...

That means you have to properly set up a request queue that doesn't overwhelm the server with 1000 requests in less than a second... (use console.log() to see how quickly your code wants to send requests...), you can do that in various ways, I'm usually doing such things with a modified version of the ajaxQueue jQuery Plugin form here, it uses promises/deferred objects and I custom-added a delay option  as I'm also using it to throttle requests sometimes, the modified plugin code is included below and after plugin code you find an example that you can run yourself (open the inspector > console to see what it does, but basically it delays each request for 1000ms = 1s):

(function($) {

// jQuery on an empty object, we are going to use this as our Queue
var ajaxQueues = [$({})];

$.ajaxQueue = function( ajaxOpts, queueIndex ) {
    var jqXHR,
        dfd = $.Deferred(),
        promise = dfd.promise(),
        ajaxQueue;

    // allow multiple queues that run independently of each other
    // specify the queue to be used like this (index can be ommited!):
    // $.ajaxQueue({<ajaxOpts>}, <int|queueIndex>)
    queueIndex = queueIndex || 0; // get queue index if specified
    ajaxQueue = ajaxQueues[queueIndex];

    if ( ajaxQueue == undefined || !(ajaxQueue instanceof $) ) {
        ajaxQueue = ajaxQueues[queueIndex] = $({});
    }

    //  if there is no ajax request return an empty 200 code
    if ( typeof ajaxOpts == "undefined" ) {
        return $.Deferred(function() {
            this.resolve( [ '', '200', jqXHR ] );
        }).promise();
    }

    // run the actual query
    function doRequest( next ) {
        setTimeout(function() {
            jqXHR = $.ajax( ajaxOpts );
            jqXHR.done( dfd.resolve )
                .fail( dfd.reject )
                .then( next );
        }, ajaxOpts.delay||0);
    }

    // queue our ajax request
    ajaxQueue.queue( doRequest );

    // add the abort method
    promise.abort = function( statusText ) {

        // proxy abort to the jqXHR if it is active
        if ( jqXHR ) {
            return jqXHR.abort( statusText );
        }

        // if there wasn't already a jqXHR we need to remove from queue
        var queue = ajaxQueue.queue(),
            index = $.inArray( doRequest, queue );

        if ( index > -1 ) {
            queue.splice( index, 1 );
        }

        // and then reject the deferred
        dfd.rejectWith( ajaxOpts.context || ajaxOpts, [ promise, statusText, "" ] );
        return promise;
    };

    return promise;
};

})(jQuery);


$(function() {
	// just for demo purposes, this would be your $.each()...
	for (var i=0; i<10;i++) {
		$.ajaxQueue({
			url: 'https://httpbin.org/get',
			delay: 1000
		}).done(function(data) {
			console.log('success');
			console.log(data);
		}).fail(function() {
			console.log('failed');
		});
	}
});