Synthesis of 1-naphthaleneacetic acid: Methods
If you have read the reference 1 carefully, you would realized that the amounts of $\ce{KBr}$ and $\ce{Fe2O3}$, as well as reaction temperature and time is very important to the reaction yield. That's the reason I asked you to list your procedures so that we can analyzed them and suggest some changes. Well, as reference 1 listed, follow the following procedure exactly and see the results:

Naphthalene with 0.0010% iron $(\pu{57.6 g},\ \pu{0.449 mol})$, chloroacetic acid $(\pu{14.1 g},\ \pu{0.149 mol})$, ferric oxide $(\pu{87.6 mg},\ \pu{0.549 mmol})$, and potassium bromide $(\pu{420 mg},\ \pu{3.53 mmol})$ were placed in a long-necked round-bottom flask fitted with a rubber stopper carrying a thermometer and an air-cooled tube about a $\pu{1 m}$ long, and the mixture was boiled gently on a sand bath for twenty hours. The best yield was obtained when the heating was controlled according to a temperature-time curve in which the temperature of reactants attained $200^\circ$ after ten hours and $218^\circ$ after twenty hours. After the reaction, a greater part of the unreacted naphthalene $(\pu{43 g})$ was recovered by distillation. The residue was extracted with hot sodium hydroxide solution, cooled, and filtered. Acidification of the filtrate with hydrochloric acid yieldeed the brownish precipitate, $\pu{19.4 g}$ (70%), m.p. $108-113^\circ$ ....

It is noted that the melting point can be raised to $132^\circ$ by repeated crystallization. First crystallization the crude product with 250-fold distilled water has yielded $\pu{9.5 g}$ of product with m.p. $124-126^\circ$. This yield is 34% based on  chloroacetic acid used, which is the limiting reagent and has reacted completely, and 45% based on naphthalene reacted.
The condition described above is the optimum conditions regarding to temperature, time, increased amount of $\ce{KBr}$, and the amount ratio of naphthalene to chloroacetic acid. Also note that:

In the absence of $\ce{KBr}$ and $\ce{Fe2O3}$, no naphthaleneacetic acid was formed.
In the absence of $\ce{KBr}$ but the presence of $\ce{Fe2O3}$, only 3% of naphthaleneacetic acid was formed.
In the absence of $\ce{Fe2O3}$ but the presence of $\ce{KBr}$, only 4% of naphthaleneacetic acid was formed.
$\ce{KBr}$ is the most effective additive for the reaction. The promoting action of several other metallic halides such as $\ce{NaCl},$ $\ce{KCl},$ $\ce{KI},$ hydrated $\ce{AlCl3},$ hydrated $\ce{AlBr3},$ hydrated $\ce{FeBr3},$ and $\ce{HgBr2}$ when mixed with $\ce{Fe2O3}$ in place of $\ce{KBr}$ was also observed but they are less effective than $\ce{KBr}$.

References:

Yoshiro Ogata and Jiro Ishiguro, &quot;Preparation of $\alpha$-Naphthaleneacetic Acid by the Condensation of Naphthalene with Chloroacetic Acid,&quot; J. Am. Chem. Soc. 1950, 72(9), 4302 (https://doi.org/10.1021/ja01165a533).