What assurance can you give me that my sins are atoned for by my repentance? I dont feel as if they are. What if there is none until I am able to offer a sacrifice at the Temple- which could not be in my lifetime, judging on the current politics. Can you assure me?

The Rambam (Maimonides) in his book Laws of Teshuvah (1; 3) writes that nowadays when there's no temple and offerings, Teshuvah (repentance) will atone for all sins regardless to how severe they may be. One surly has to be sincere with his Teshuvah, but if one repents properly Hashem through the prophet's promised us he will except our repentance, and will atone our sins. Some sins require additional factors for full repentance, like sufferings and Yom Kippur (ibid 4), but as stated atonement is promised.