Some basic question about using Arduino’s ICSP programmers. I would appreciate some help about this

How to buid and use programmers to program Arduino’s is a article plenty explained, and how in the past I never used ICSP programmers with arduino sketch, I wonder myself about the idea of build and use a programmer arduino as ICP (32u4) pro-micro board to program other Atmega32u4 similar board.. I would like to use Atmega32u4 as it has 25% more sram than the 328P although less flash is available from the internal USB. If my design is standalone, the USB would not be necessary other than to program from arduino with bootloader. From here, I think that overriding the bootloader by uploading the sketch using ICSP, I could dispose 4096 more bytes for the sketch. Is this so correct? Could I have really 32768 Bytes of flash for improve the sketch? And more questions: Would the tx, rx pins be available as ttl rs-232 for my standalon layout? At present I am designing a sketch for Atmega32u4 trying to dedicate all flash memory available. I’m currently testing a pro-micro board with a sketch that integrates a 128×64 pixel oled display in text mode using the u8x8 library, an SD card module that performs operations with files from command line arduino terminal, a HC-05 bluetooth module to turn on/off LEDs from mobile phone, and a manual rotary encoder to dispatch orders from the oled display using external ISR. At the moment I’m in the limit (99%) of the available flash memory of 28000 bytes. With intention of taking advantage of all available flash memory space (32736 bytes) I built a programmer Arduino As ICSP (32u4) using a pro-micro module. Everything works fine, but I can’t find the way that the compiler recognizes additional 4096 bytes flash memory available when uploading the sketch from the programmer. This does not allow me to move forward incorporating more code in new functions.Any suggestions in this regard would be greatly appreciated. Thanks.

Can you please edit your post to separate the questions and their supporting statements into paragraphs.
Otherwise, this is very difficult to read.

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Bullets and separating ideas is helpful. Continuous text is not only difficult to read but for those of us who are more graphical it is less likely to even be read.

Google for “ATmega32u4 fuses”
The fuses reserve a section for the bootloader. You can use Avrdude so set these. You also have to modify the entry in the boards.txt file in the IDE for your board or, better, create a copy and rename/modify that. Look for an entry similar to this :
leonardo.upload.maximum_size=28672

Thank you very much 6v6gt, your advice, Google for “ATmega32u4 fuses” was of great value. I found a recent very helpful post on the forum: “Removing bootloader ATMEGA32u4”. Thank you