Irregular bleeding after IUCD

Q: I got a procedure of IUCD for contraception on July 1, 2019. It was important as per doctors instruction due to some medicines with which I cannot conceive at the moment. The gynaecologist said that in the start I will face some extra/heavy bleeding or irregular spotting due to this.

My previous routine of periods was 8 days except for Ramadhaan i.e. 9 days. My old dates for 2019 were

17 Jan - 25 Jan
12 Feb - 20 Feb
11 March - 19 March
7 April - 15 April
2 May - 11 May
30 May - 7 June
Important one (25 June - 5 July)

My questions are:

1. I took a bath after 10 days completion in my last cycle i.e 25 June to 5 July due to spotting as maximum days for periods are 10 days but still I got spotting for 3 more days. I offered my salaah and Quran. Was this calculation ok?

2. I started spotting again on 16 July but as per my last cycle, there wasn't a gap of 15 days in between two cycles. I am still having light spotting plus bleeding. I am offering salaah and Quraan with fresh wudhu everytime. Am I correct?

3. If in the last cycle I consider it to be 8 days then 25 June - 3 July then after 18 days of habit I must be having periods on 21 July, so what should I do? How would I calculate that either its istihaaza or periods? 

Intention of different nafl salaah when performing one nafl salaah

Q: I came to know by one of the dawat-o-tabligh elders that we can make intention of many different namazes (e.g: if we are praying ishraq then we can make intention of tahiyaatul wudhu, tahiyyatul masjid, salaatul hajat, salaatul taubah, etc.)

1. Is it true?

2. How many total extra niyyats can we make for a two rakat nafil?

3. Can we do the same for zohar, maghrib and isha nafl prayers?