I think Doubledee explained it well but I'll add my own thoughts to. If I understand your example right.

Interest, therefore, becomes firmly established in a way that it no longer appears as a division of gross profit of indifference to production, which occurs occasionally when the industrial capitalist happens to operate with someone else's capital. His profit splits into interest and profit of enterprise even when he operates on his own capital. A merely quantitative division thus turns into a qualitative one. It occurs regardless of the fortuitous circumstance whether the industrial capitalist is, or is not, the owner of his capital. It is not only a matter of different quotas of profit assigned to different persons, but two different categories of profit which are differently related to the capital, hence related to different aspects of the capital.

Vol 3 Chapter 23

I cite that because as you said, 5% of that goes back to the lender and over time that will repay the original money capitalist. Or that portion for the money capitalist. It just a manner of proportions in regards to that surplus value or profit to who gets what of that total surplus value produced.

The industrial capitalist preserve his 120 capital like he would if the money capitalist never came along. Since Marx mentions in a few others chapters, one of the goals of labor power is not to just produce surplus value, but also to recreate/preserve the already existing value. So that 120 capital is recreated back into the new commodities made along with surplus value. And that is still the same even when the money capitalist comes along. And when the money capitalist does come along, it just a matter of proportion for the profits or the total surplus value that was produced, they each get. Nothing to do with the preservation of the already existing capital value. And the constant capital does depreciate.

To cite something way back from Vol 1, chapter 8

[...]He is unable to add new labour, to create new value, without at the same time preserving old values, and this, because the labour he adds must be of a specific useful kind; and he cannot do work of a useful kind, without employing products as the means of production of a new product, and thereby transferring their value to the new product. The property therefore which labour-power in action, living labour, possesses of preserving value, at the same time that it adds it, is a gift of Nature which costs the labourer nothing, but which is very advantageous to the capitalist inasmuch as it preserves the existing value of his capital. [4] So long as trade is good, the capitalist is too much absorbed in money-grubbing to take notice of this gratuitous gift of labour. A violent interruption of the labour-process by a crisis, makes him sensitively aware of it