Dependance of Jiva on Shri Ramchandra

 सीतानाथ समारम्भां रामानन्दार्य मध्यमाम्। अस्मदाचार्य पर्यन्तां वन्दे श्रीगुरू परम्पराम् ।।

Jagadguru Bhagvan Ramanandacharya while commenting on the very first word “Ishavasya” of Ishavasya Upanishad says:

ब्रह्मविद्योपदेशाय प्रवृत्तायामस्यामुपनिषदि प्रथम तः स्वतन्त्रात्मतादिभ्रमवन्तं संसारानलपरितप्तं तत्त्वजिज्ञासया शरणमुपागतं शिष्यं प्रति तादृशभ्रमनिवृत्ति फलकं सर्वस्य भोक्तृभोग्यवर्गस्य परमपुरुषाधीनत्वं मुमुक्षोचितांवृत्तिञ्च गुरुरुपदिशति—ईशेति

The teaching of Brahmavidya is imparted in this Isha Upanishad to the disciple who is initially under the misconception that the “Individual soul is independent”, and who is distressed by the burning fires of the cycle of life, comes to seek refuge with a desire to understand the truth. This is the essence of the teaching in the Ishavasya Upanishad. 

The refutation of such heavy misconceptions is taught by the guru through the instruction of the Upanishads and revealing the ultimate truth of the Supreme Being's sovereignty over the enjoyer and the enjoyed, and guiding the way to liberation. This is explained through passages like "Isha Vasyam". (-Ishavasya Upanishad Anand Bhashya 1.1)

And Srimad Goswami Tulsidas has followed same what His Parmacharya Bhagvan Ramanandacharya has said, He writes:

परबस जीव स्वबस भगवंता। means Jiva is completely dependent on sri raghunandan and sri raghunandan is completely independent. 

परम स्वतंत्र न सिर पर कोई। भावइ मनहि करहु तुम्ह सोई॥  You are supremely independent, with no one above you. Whatever pleases the mind, that's what you do.

Bhagvan Ramanandacharya refuted the notion that the individual soul is independent, whereas Goswami Tulsidas Ji, in his Ramayana, writes that the soul can never be independent. This is why the Isha Upanishad begins with the word "Ishaavaasya," which clearly demonstrates that everything is under the control of Lord Sri Ram. No one is above Him, and no one is independent of Him; everyone is subservient to Him.

See, As per Ramanandacharya Srimad Goswami Tulsidas Ji has taken a vow in Ramcharitmanas that, “नानापुराणनिगमागमसम्मतं- श्लोक ७” means this Ramayan will be strictly in accordance with Vedas, Puranas, Aagamas etc. So how he can write a inch beyond that? The question that you have asked is a pure vedic concept and lies under Vishishtadvaita Philosophy which was propounded by Goswami Tulsidas in his works. Let's see what Sri Goswami has said;

ब्रह्म जीव सम सहज सँघाती ॥

The two letters ‘Ra’ and ‘M’ are naturally existing together as Brahm and Jiva.

And how Brahm and Jiva are existing together? It has been explained in Rig Veda:

द्वा सुपर्णा सयुजा सखाया समानं वृक्षं परिषस्वजाते ।
तयोरन्यः पिप्पलं स्वाद्वत्त्यनश्नन्नन्यो अभिचाकशीति ॥ १ ॥

Two birds (Jive & Brahm) living together, each the friend of the other, perch upon the same tree of these two, one eats the fruits of the tree, but the other simply looks on without eating. (-Rig Ved 1.164.20)

Brahman always resides with the individual soul (jiva) and watches over it, but the consequences of actions (karma-phala) are experienced only by the individual soul, not by Brahman. This is the same relationship that Goswami Tulsidas ji has explained in Ramayan. Here you need to understand in Vedas, Brahm has been said as Sakhā or friend of Jiva and this is also clear in Srimad Ramcharitmanas;

स्वारथ रहित सखा सबही कै ॥ Sri Raghunandan is selfless friend to all. (-Srimad Ramcharitmanas Ayodhya Kand 74.6)

And don't get confused that Brahm and Jiva are living together, it does not mean that they are one! Clearing this doubt Bhagvan Ramanandacharya has said in Mandukya Upanishad 3.1.1 commentary as this Rigved 1.164.20 mantra has been repeated there;

अत्र तयोरन्योऽनश्नन्नन्यः इत्युभयथा जीवपरमात्मनोर्भेदः प्रदर्शितः तेन जीवः परमात्मापेक्षयाऽत्यन्तं भिन्न इति दृढीक्रियतें तस्मात्पराभ्युपगतं जीवब्रह्मणोरैक्यं निरस्तं वेदितव्यम् ॥१॥

The statement 'तयोरन्य:' -'अनश्नन्' expresses the distinction between the individual jiva and the Paramatma, highlighting their differences. Thus, the individual soul is considered significantly separate from the ultimate reality. Therefore, the viewpoint of those who perceive complete non-difference between the individual soul and the ultimate reality contradicts the teachings of the Vedas and scriptures, making their belief highly contradictory.

(-Mandukya Upanishad Ananda Bhashya 3.1.1)

And even Sri Goswami has said has expounded the same concept of His Parmacharya, Bhagvan Ramanandacharya that jiva is completely dependent on Brahm: परबस जीव स्वबस भगवंता। means Jiva is completely dependent on sri raghunandan and sri raghunandan is completely independent and also: 

ईस्वर अंस जीव अबिनासी। which means Jiva is the portion of Bhagvan Sri Ram and is eternal. Hence they are not one.

According to Vishistadwait Philosophy Jiva and Brahm are not one.